What self-propelled device did Leonardo da Vinci design with a coiled spring as its power source?

Leonardo da Vinci designed a self-propelled cart powered by coiled springs.

The cart used stored mechanical energy rather than animal power, gravity, or an external push. Springs hidden inside the chassis would be wound before operation and then released to turn the wheels through a system of gears and transmission components.

Leonardo’s drawing, made around 1478 to 1480, shows a compact vehicle with a steering arrangement and a mechanism for controlling its movement. The cart may have been intended for theatrical performances or court spectacles rather than transportation over long distances.

It is often described as an early robot or automobile, but those labels can mislead. The machine was not powered by an engine and was not designed as a practical road vehicle. Its importance lies in the use of stored spring energy for autonomous movement.