Without the need to punch thru armour there's little call for a powerfull bow, the rise of the 100lb+ bows was due to there use in warfare.

Jean Henri Chandler wrote:

Depends what you mean by "makes a casualty". we know from various period literary sources (ranging from personal letters to formal records), that wounds of a fairly trivial nature were very common in medieval warfare. Nor does the modern trope that (in the middle ages) any kind of open wound down to a paper cut automatically lead to death by infection hold up to scrutiny.

I mean the solid incapacitating wound, like an arrow thru an extremity, something that is likely to effect your ability an will to fight.
If poison mean that such a wound is a lingering issue needing more treatment or just the fear of poison means demands preventative actions then it worked.

Jean Henri Chandler wrote:

2,000 + years of their use in China and elsewhere suggests that it did make a difference.

China has access to better poisons, The Chinese cobra is far more deadly then anything in western Europe.

Jean Henri Chandler wrote:

But there did eventually develop enough of a cultural prohibition against their use that it has certainly diminished. Maybe something like that happened with poison weapons by the medieval period. But maybe it's use did continue here and there in some fashion, much as we see Chlorine and Sarin and so on showing up on modern battlefields. That's what I'm interested in finding out at this point.

I think that useing poisoned weapons was a bit like being a flame thrower operator, your hated an despised by your foes, you often will not be taken prisoner.
Given how poison is often seen as cowardly and indiscriminate.

Jean Henri Chandler wrote:

Molten glass being dumped over the side of a wall in a siege is extremely risk.

That's a new one do you have a source for that?

Another example of European contact with effective poisoned weapons would be the 17th-century Dutch experience in Makassar. I know about this through Daniel Carey's article "The Political Economy of Poison: The Kingdom of Makassar and the Early Royal Society." Dutch soldiers who faced Makassarese soldiers greatly feared blowpipe darts & other weapons poisoned with Antiaris toxicaria. Makassarese soldiers attached blades smeared with poison to their blowpipes & used them like spears to good effect. Some accounts claimed these poisoned weapons killed instantly or very quickly, while others indicated incapacitation within half an hour & death within an hour. Europeans tried to figure out how this poison worked in the 17th & 18th centuries, but with little success.

The case supports the notion that medieval & Renaissance Europeans made limited use of poisoned weapons in warfare in part because the most potent poisons were difficult if not impossible to produce in Europe (Antiaris toxicaria doesn't grow in Europe, for instance) & that poison production wasn't easy. Places that made effective military use of poisoned weapons seem to have had access to plants or animals with powerful toxins. If only lower-quality poisons were available in Europe, as seems to be the case, that goes a long way toward explaining the limited military use of poisoned weapons. Less potent poisons would be less likely to be worth the trouble to add to military arrows/bolts/darts, which were generally made rather cheaply & in large numbers.

In the case of Antiaris toxicaria, according to Carey's article, 17th-century Europeans who investigated the poison failed to even successfully use it in Europe. The Royal Society of London repeatedly conducted experiments that showed little or no effect but couldn't but sure they were getting real or effective Makassarese poison; Charles Howard, who'd been to Makassar, said the poison only remained potent for a month. Thus, the samples shipped to England had already lost their power by the time they arrived.

While it's theoretically possible the British Empire or some other European power could have employed poisoned weapons imported from Makassar in Europe in 17th century, they certainly didn't demonstrate the ability to do so in practice. The care required in preserving the poison apparently made transportation over thousands of miles tricky. Presumably there would have been some way to transport the materials & prepare the poison in Europe, but this didn't happen in the 17th century. There were lots of bogus & fanciful tales about the poison & how to cure it.

Jean-Baptiste Leschenault dispeled the myths & provided more accurate information about Antiaris toxicaria in 1810.

I'm not sure if I follow your point here.

This is just one very specific poison from one specific, and very remote place. I believe they had similar problems trying to figure out some of the poisons used in the Amazon, derived from frogs. So what?

Makassar is 11,000 km from Rome. Tunis, by contrast, is a much more convenient 1,200 km. In Tunisia one can find Egyptian cobras and 6 different types of poisonous vipers, plus poisonous scorpions.

Many poisons were very common in Europe through the medieval and Early Modern period. This includes arsenic which I've mentioned several times, and has a very long history of widespread use in Europe ...

https://sites.dartmouth.edu/toxmetal/arsenic/arsenic-a-murderous-history/

... to many other types including other minerals like cinnabar, malachite, and chalcanthite, other well known natural poisons such as hemlock, foxglove, cyanide (which can be derived from cherry pits among other common sources), various mushroom derived poisons, and so forth.

The seeds of this strychnine producing tree from India were apparently specifically used to make poisons for arrows:

https://en.wikipedia.org/wiki/Strychnos_nux-vomica

The seeds are apparently stable and remain potent for a long time.

So the idea that poisons were in any way rare in Europe is ridiculous.

The only question is regarding the use of poisons specifically with weapons, which was apparently done by the Romans. It may or may not have fallen out of use, though I've not seen any evidence either way at this point.

Antiaris toxicaria is example of dart/arrow poison that proved effective for military use in large numbers, both in Southeast Asia & in China. A number of historical & more recent tests confirm its potency, as I've gone over a bit. It seems to be able to incapacitate in a reasonably short amount of time, depending on the dose.

Europeans indeed had some access to & familiarity with projectile poisons, particularly for hunting, but that doesn't necessarily mean these would have been as useful for warfare or that it would have been economical to add poison to military arrows in sufficient numbers. Snake venom was used on projectiles in various contexts, from South Asia to North America, but importing enough venom from Tunisia (or whatever) seems prohibitively expensive at best. Renaissance England, at least, made arrows relatively cheaply & didn't give each archer all that many of them, according to available records. (Roger Ascham complained about the wood choice for common military arrows.)

European ingested poisons weren't always effective; Antonio Pérez poisoned Juan de Escobedo two or three times without the desired fatal effect. Pérez & the Spanish king ended up just having Escobedo killed by the sword.

Cheng Zong You's crossbow manual presents itself as offering a relatively cheap & easy away to equip & train farmers to fight. He mentioned that the crossbow with a bamboo prod was economical & average people could use it. So apparently he considered making poison from Antiaris toxicaria & Anconitum ferox cheap enough for ordinary farmers turned soldiers.

Even in China, where Cheng's manual suggests very potent poison was cheap enough for farmer soldiers to use, poisoned projectiles probably weren't standard. Mention of poison projectiles does seem to appear in the context of ones they wouldn't be effective otherwise, such as Cheng's explicitly weak crossbows & the famous repeating crossbow. If Cheng's claims are true, it seems every projectile should have been poisoned, but I'm not aware of evidence for that. Perhaps it was more expensive &/or less effective than Cheng asserted.

I guess there are multiple possible explanations for the lack of sources on weapon poison in medieval Europe. Perhaps it saw more use than the sources indicate. Perhaps cultural factors & agreements on how to fight limited it. Perhaps economics limited it, including lack of access to cheap & effective weapon poisons. Perhaps it was some combination of these.

Almost no poison is 100% effective. Even modern Russian attacks with radioactive poisons haven't always worked.

I have said this already a couple of times in this thread, so I am probably getting tedious, but I'll say it again, I think given the volume of all kinds of merchandise imported from China, Persia, India, Central Asia, and the Middle East, not all of it immensely valuable, from dyes to incense to weapons textiles and food stuffs down to pet animals and pastries, it's absurd to think they couldn't have imported anything they needed for poisons if they wanted to. In fact we do know that they imported orpiment and realgar (both arsenic ores) which were used as tints in painting and as medicines. In greater concentrations of course they make strong poisons and the Chinese in fact coated arrows with them, apparently.

As an example, I'll list some of the merchandize discussed in the Pratica della Mercatura, written by a Florentine merchant named Francesco Balducci Pegolotti, who worked for the Florentine trading firm of Bardi. Goods listed as being traded to the Chinese: wax, tin, copper, cotton, madder, cheese, flax, and oil, honey, saffron, raw amber, amber beads, vair-skins, ermines, foxes, sables, fitches and martens, wolf skins, deerskins, and all cloths of silk or gold, pearls, wheat, Greek wine and all Latin wines “sold by the cask”. Malmsey and wines of Triglia and Candia “sold by the measure”. Caviar “sold by the fusco, and a fusco is the tail-half of the fish's skin, full of fish's roe”. Suet “in jars”, iron “of every kind”, tin, lead, zibibbo “or raisins of every kind, and the mats go as raisins, with no allowance for tare unless they be raisins of Syria. In that case the baskets or hampers are allowed for as tare, and remain with the buyer into the bargain”. Soap of Venice, soap of Ancona, and soap of Apulia “in wooden cases. They make tare of the cases, and then these go to the buyer for nothing. But the soap of Cyprus and of Rhodes is in sacks, and the sacks go as soap with no tare allowance”.

The goods purchased in China include raw silk, silk-gauze, dressed silk, ginger, cubebs, lign-aloes, rhubarb; mace, long pepper, ladanum, galangal, broken camphor; nutmegs; spike , cardamoms, scam-mony, pounding pearls, manna, borax, gum Arabic, dragon's blood, camel's bay, turbit, sweet-meats, gold wire.

I would say if they can bring cheap soap from Cyprus, and suet and raisins to China, and bring back gun Arabic, rhubarb, ginger in sufficient quantity that practically all of Germany made gingerbread cakes in December, then they could bring back some venom if they needed to.

As I noted (again, sorry to repeat myself) they brought sulfur all the way from Iceland to make gunpowder. Tunisia is an easy trip by comparison (dozens of ships from Tunis arrived in multiple ports in Italy almost every day unless there was an active war preventing it).

I am not saying anything about the large scale, systematic use of poisoned arrows or any other special chemical or biological weapons in Europe in the middle ages. I don't know of any evidence pro or con on this past the era of Imperial Rome. I am just pointing out the possibility can't be dismissed out of hand on the basis of simplistic claims like "they couldn't afford it" or 'they didn't have poisonous snakes" or "it was too hard".

And for that matter, I'm not sure there is any lack of written evidence in the sources. Literal tons of medieval manuscripts haven't been even read yet let alone transcribed or translated, and many that have been transcribed and analyzed are still unknown as the papers about them remain obscure. All we can say is that the summaries in the 19th and early 20th Centuries don't seem to say much about their use in Europe after the Roman period. But they skipped and omitted a lot of stuff, like the existence of martial arts in Europe.

There were all kinds of special ammunition used with bows, crossbows and firearms. And some weapon types which for a long time people have speculated may have been intended for use with poison, like the so called balestrino.

One late-medieval source that shows at least familiarity with poisoned weapons is a surgery manual by Hieronymus Brunschwig. In the 1525 English translation, the text mentions poisoned arrows & similar & how to treat a patient wounded by such. I'm not sure exactly when the original was published, but Brunschwig died in 1512, so at least the majority of his life & practice was at the end of the medieval period.

Edit: The original was published in 1497. The 1525 English isn't too clear to me, so checking out the original might be useful if anyone has access.