What Leonardo da Vinci invention used a coiled spring to move itself across the ground?

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

The cart appears in drawings from the late 15th century and is often described as a programmable ancestor of the automobile or robot. Two large leaf springs stored energy, while a system of gears transferred that energy to the wheels. A steering mechanism could be set in advance, allowing the cart to follow a predetermined path.

The machine was probably intended for theatrical or ceremonial use rather than transport. Some researchers connect it with court festivities in Renaissance Italy, although the precise event for which it was designed is not certain. Leonardo left no complete construction manual, so modern versions rely on interpreting his sketches.

In 2006, an Italian team built a working reconstruction based on the drawings. The cart could move without a person pushing it, but it was not powered by an engine and could not be steered freely while moving.