What self-propelled machine did Leonardo da Vinci design using a spring-powered mechanism?

Leonardo da Vinci designed a self-propelled cart powered by coiled springs and controlled by a programmed mechanism.

The cart appears in drawings from the late fifteenth century. Two large leaf springs stored energy, while gears transferred that energy to the wheels. A system of cams acted like a simple program, determining how far the cart would travel and allowing its path to be set before release. The design has therefore been called an early robot or an ancestor of the automobile, although both labels are modern interpretations.

Leonardo may have intended the machine for theatrical displays at court, where it could move without an obvious person pushing it. The original device has not survived, so details must be reconstructed from the drawings and notes.

A major reconstruction was built in the early 21st century by researchers and engineers, who demonstrated that the design could move when made with historically plausible materials. It was not powered by fuel and could not steer like a modern car.