Which Leonardo da Vinci invention was a four-wheeled vehicle powered by wound springs?

Leonardo da Vinci's four-wheeled vehicle powered by wound springs is called the self-propelled cart. He designed it around 1478–1480, making it one of his earliest known studies of autonomous mechanical movement. The cart used coiled springs to store energy, while a programmed system of cams controlled its path.

Unlike a normal carriage, the cart did not require a horse or a person to push it continuously. Its front wheel could be set to determine a curved route, and the mechanism could make the vehicle move for a limited distance after the springs were wound. This made it a mechanical demonstrator as well as a possible theatrical prop.

The surviving drawing is incomplete and does not provide every construction detail. In 2006, engineers in Florence built a reconstruction based on Leonardo's plans, and it operated successfully. The cart is sometimes called the first robot or the first automobile, but those labels are modern comparisons rather than names Leonardo himself used.