Those familiar with sword technique or even medieval military history will recognize the name Talhoffer, one of the firsthand sources used by historians, experimental archaeologists, and by HEMA practitioners to revive medieval fighting techniques.
However, he also included in his illustrations some very bizarre inventions, including a medieval tank and a device called "The Crayfish" which used blades and bombs to guard gateways.
This documentary is really well worth the watch, and it's given me a thought: I should really push the envelope with "The Linen Butterfly." I thought I was being bold by giving my characters access to handgonnes (a sort of cannon on a stick that predates the arquebus) as I had subverted a very old trope about not having guns in fantasy stories, but this just takes it to a whole new level. Granted, this is 15th century and "The Linen Butterfly" is more based on the 14th century, but I really want to add some things the reader won't expect.