What weapon did Leonardo da Vinci design with a bow described as 42 braccia wide?

Leonardo da Vinci designed a giant crossbow with a bow described as 42 braccia wide.

The weapon appears in Leonardo’s military engineering drawings from the late fifteenth century. Its enormous bow was intended to launch large bolts or stones and to create a frightening visual effect on the battlefield. Leonardo also drew a wheeled base and mechanisms for drawing the bowstring, because a weapon of that scale could not be operated like an ordinary handheld crossbow.

The braccio was an Italian unit whose exact length varied, so 42 braccia does not convert to one universally agreed modern measurement. The design was probably intended as a siege weapon, where size and intimidation could matter as much as practical rate of fire.

There is no firm evidence that Leonardo’s giant crossbow entered military service. It belongs to a group of ambitious weapons he proposed while seeking employment from powerful patrons. The design is often confused with his multi-barreled cannon studies, but the crossbow used stored mechanical tension rather than gunpowder.