The Munich manuscript of Mair’s De arte athletica is online here. Splendidly illustrated, this manuscript is written in Latin, in a very legible humanist hand. The illustrations show a fencing school rather than combat in earnest: the specialized longsword foils are clearly illustrated, and lance combat on foot is fought with headless shafts. Dusacks, wooden or hardened leather simulators of messers or cutlasses, are also clearly shown: note the additional protection over the knuckles.
The manuscript also shows combat with sickles and scythes, which looks pretty scary. I’m still looking for discussion of combat with millstone-handles, the other traditional martial art developed by the Swabian peasantry to resist their feudal overlords.
The Higgins Armory Sword Guild has transcription, translation and interpretation of several of Mair’s sequences for longsword on their site.