What huge artillery weapon did Leonardo da Vinci design with a single bow?

Leonardo da Vinci designed a giant crossbow, a huge artillery weapon intended to launch large projectiles.

His design had an exceptionally broad bow mounted on a wheeled or supporting frame. A winding mechanism would draw the bowstring back, storing energy before release. The large scale was intended to increase the weapon’s psychological impact and throwing power.

Leonardo’s crossbow was a concept recorded in drawings rather than a weapon known to have entered regular military service. Renaissance military engineers often proposed imposing machines whose construction and battlefield value were uncertain.

This weapon is distinct from Leonardo’s multi-barrel organ gun and from ancient ballistae. The giant crossbow used a bow and string, while those other machines followed different projectile-launching designs.