In Leonardo da Vinci’s self-propelled cart, what stored energy drove the wheels?

Leonardo da Vinci’s self-propelled cart was driven by coiled springs. His drawings show a three-wheeled vehicle whose spring-powered mechanism could make it move without an onboard driver or animal.

The cart is often described as an early ancestor of the automobile and, more specifically, as a machine capable of programmed movement. The springs were wound before operation, storing mechanical energy that was released through a system of gears and controls.

Leonardo probably designed the cart for theatrical or ceremonial use rather than ordinary transport. Reconstructions have demonstrated that the design can function, although details in the drawings require interpretation. It was not powered by an engine, fuel, battery, or steam: its motive force came from wound springs.