Leonardo da Vinci's spring-powered stone-throwing machine was a catapult. His military notebooks include improved catapult designs that use stored mechanical energy to propel a projectile toward a target.
Leonardo studied older siege engines and tried to make them more powerful, reliable, and easier to operate. Some of his designs used large curved leaf springs, while others relied on a winding mechanism and a throwing arm. The drawings show how he analyzed force, leverage, and the movement of mechanical parts.
Leonardo's catapults were proposals rather than documented battlefield successes. They belong to a long tradition of siege artillery that predates gunpowder weapons. The word “catapult” covers several types of machine, so not every historical catapult used the same spring or arm arrangement.
This design should not be confused with Leonardo's giant crossbow. A catapult throws a projectile with a swinging arm, while a crossbow stores energy in a bent bow and releases it through a string.