Did any of the Italian or Spanish masters discuss the use of the rapier from horseback?

Obviously the rapier was a civilian weapon and never intended for use by the cavalry (although Patton might've suggested it had he been alive at the time). Nevertheless, I assume that men of the rapier period would have had occasion to travel on horseback as civilians. I also assume that the roads were no safer than the streets of the period and civilian defense would have been a relevant concern. Would civilian travelers of the time relied on rapiers for mounted defense, and if so, were there codified teachings covering such use?

Gustavus Adolphus carried a sword in battle as did all military men of the period. The notion that he used a rapier is due to a mistranslation of the Swedish word "värja" which in todays usage is the Swedish word for "rapier". In the 17th Century however the word had a diffrent meaning and should be translated as "arm" or "sidearm". The Swedish word for rapier in that period was "rappir"

The so called "Lutzen rapier" has narrow but very strong blade that looks very much like a slimed down version of a type XVa fitted with a complex hilt.
http://s277.photobucket.com/albums/kk50/Dstab...artifacts/

Not to get too off topic, but I would argue that this:

http://s277.photobucket.com/albums/kk50/Dstab...rjahel.jpg

Isn't that different from these:

http://www.thearma.org/Manuals/Fabris/book1/04011061.jpg

Or any number of other "rapier" treatises. So if the Gustavus Adolphus sword isn't a rapier, then I don't know what we can define as a rapier. And consider that the Italians also said "sword" (spada), and didn't even use the term rapier at all. :)

But thank you for those pictures!

Well, as dad always said, "close enough for government work."

Categorization aside, the Lutzen blade seems to fit the bill. The question is, was carrying such as this common, and, if so, why don't we have texts detailing mounted use for such a weapon?

I seem to remember someone saying somewhere that estocs were used from horseback like a short lance, I imagine a rapier being usable in a not totaly dissimilar way, but I'll leave it up to others with more of a clue to comment. Only artwork I can think of that is relevent shows a chap I assume to be st George using a rapier like blade on a dragon. I am unsure as to the veracity of the image ;)

Thibault was originally planning on writing about combat with the sword on horseback, but died before he could put it into his book, Academie de l'Espee. I can only assume he would be using the same sword he used on foot, a sword that is widely considered to be a rapier since we identify Academie de l'Espee as a "rapier manual".

Yeah, and as you might have discovered, the answer to your question depends a lot on what you mean by "rapier" ;). Personally, I find the Lutzen rapier is a bit odd since it has the length of a civilian rapier (a whopping 116cm/45" total length) yet is apparently military. Do we know if this sword was intended for the battlefield? I mean, I would have gone with something a bit easier to draw and with a wider debole were I myself mounted, but who am I to criticise what an actual cavalryman might have carried?

I have always found that I can use most longswords as a rapier. The weight and balance is not to too far off. Infact, I have found that some rapiers, with all the hand protection, end up being heavier then some longswords.

A longsword is a hand and a half sword after all that can be used one handed or two handed. On foot or in the saddle. I do believe that many rapier techniques came down from earlier longsword techniques (Sprechfenster, 8 windings). I do believe that the dividing lines that seem so clear to us were historically more blurred.

I was under the impression that rapier were not just civilian weapons, so there very well maybe a book or treatise on rapier on horseback. Though it maybe a case of the book showing one weapon but it also works with rapier.
As for military rapier. I was under the impression that there were examples of swords that looked like an arming swords redone with a complex rapier hilt.
And in "The tacticks of Aelian", published in 1616 or so, it describes the idealized pikemen as armed with a 15 ft pike and rapier as a side arm. Can't remember what he thought the horseman should be armed with, most likely lance and some sort of arming sword, I would have remembered it if it was something odd.

If i may add something: from the records from Poland-Sweden wars of XVII c there's an indication of usage of long, slender blades by Swedes and Polish "foreign regiments" (cudzoziemski aurorament, these were Poles, but armed and organized on western pattern, not more 'common' eastern) As for character of those blades one can speculate - as for Polish regiments theres rapier or "waloon palash" mentioned, but there's speculation that rapier could mean just complex-hilted sword. Also I know only the secondary/tertiary works, maybe some of my more scholarly countrymen could post some more tangible data.
As for usage of "koncerz" (Tuck/Estoc-like weapon also called panzerschtecher or contus) , it was commonly used as a backup weapon for lance-bearing cavalry (hussary mostly, put also "armoured" units-"Pancerni") . There are two hilt forms for it, the sabre like hilt and "turkish hilt" . And it was definitely used from horseback. Note: Pallash is different weapon than this.
Sabre hilted: http://pl.wikipedia.org/wiki/Plik:Koncerz_Muz...%99bia.JPG
"turkish hilt" ( ones housed in Graz armoury)
and another one, combined with pistol
Something more on the subject here: http://www.kismeta.com/diGrasse/Koncerz.htm

So one might argue that is weapon quite "rapieresque" in blade shape and method of use (pure thrust), that is if one stuck with "rapier is something that can only thrust" definition, not necessarily good one

The problem here is that there's simply not much information at all about techniques for any kind of swordsmanship on horseback during the Renaissance--not just for the rapier.