What body of Leonardo da Vinci's notes contains his design for a giant crossbow?

The Codex Atlanticus contains Leonardo da Vinci's design for a giant crossbow.

The giant crossbow is one of the military-engineering projects represented in this vast collection of Leonardo's drawings and notes. The design envisioned an unusually broad bow mounted on a wheeled frame, with a mechanism for drawing and releasing the string. Its scale was intended to increase the weapon's range and psychological impact.

The Codex Atlanticus is the largest single collection of Leonardo's manuscripts. It contains 1,119 paper leaves covering subjects such as engineering, anatomy, mathematics, architecture, and flight. The name “Atlanticus” refers to the large atlas-sized sheets on which many pages were later mounted, not to the Atlantic Ocean.

The giant crossbow is not evidence of a battlefield weapon that Leonardo completed. Like many of his military projects, it was a design study. The codex is held by the Biblioteca Ambrosiana in Milan, where it remains a major source for studying Leonardo's technical ideas.