What self-propelled device did Leonardo da Vinci design using clockwork springs to move a short distance?

Leonardo da Vinci designed a self-propelled cart powered by clockwork springs to move a short distance.

The cart appears in drawings from around 1478 to 1480. Two symmetrical springs supplied stored energy, while a system of gears transferred that energy to the wheels. A steering mechanism could set the cart to follow a prearranged path, making it more than an ordinary hand-pushed wagon.

The machine was not an automobile in the modern sense. It had no engine, fuel system, accelerator, or means of continuous propulsion. Its stored-energy mechanism was closer to a large spring-driven clock or theatrical automaton. The design may have been intended for stage effects or ceremonial displays.

A full-scale reconstruction built for a 2006 exhibition in Florence demonstrated that the mechanism could work. The cart is sometimes called Leonardo’s robot because a later reconstruction helped power a mechanical lion, but the cart itself and the lion automaton are separate designs.