A series of 16th-century manuscripts that have been making waves on the Internet look like a Monty Python version of the Renaissance: They show cats outfitted with flaming backpacks, attacking castles and villages.

But the illustrations are legit. They're intended to show how cats and birds could in theory be used to set fire to a besieged city, according to a University of Pennsylvania scholar.

Fraas translated from the original German:

"Create a small sack like a fire-arrow ... if you would like to get at a town or castle, seek to obtain a cat from that place. And bind the sack to the back of the cat, ignite it, let it glow well and thereafter let the cat go, so it