Which Leonardo da Vinci invention used gears to move without a driver?

Leonardo da Vinci's self-propelled cart used gears and springs to move without a driver.

Leonardo designed the cart around 1478–1480, making it one of his earliest known mechanical projects. Two symmetrical 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 rather than being guided by a person during movement.

The device is sometimes described as a robot or automobile, but those labels can be misleading. It had no engine, computer, or ability to respond to its surroundings. It was a programmable mechanical automaton: its movement was determined by the arrangement of its springs, gears, and steering components.

A working reconstruction was displayed at the 2006 Leonardo exhibition in Florence. The cart may also have been intended for theatrical effects, such as appearing to move by itself during court performances.