What machine did Leonardo da Vinci sketch to move itself without an external animal or person?

Leonardo da Vinci sketched a self-propelled cart powered by wound springs rather than by an external animal or person.

The machine appears in drawings from the late fifteenth century. Two large springs stored energy, while gears transferred that energy to the cart's wheels. A steering mechanism could be set in advance, allowing the vehicle to follow a predetermined path rather than being guided continuously by a driver.

The cart is often described as a predecessor of the automobile, but it had no engine in the modern sense. Its power came from mechanical spring tension, much like a large clock mechanism. The design may have been intended for theatrical displays or court festivities.

A full-size reconstruction was built for a 2006 exhibition at the Museo Nazionale della Scienza e della Tecnologia in Milan. The reconstruction showed that the mechanism could operate, although surviving evidence cannot prove exactly how Leonardo intended every part to function.