What did Leonardo da Vinci’s self-propelled cart use to store its driving power?

Leonardo da Vinci’s self-propelled cart used coiled springs to store its driving power.

Leonardo designed the cart around 1478–1480. Its two large wheels were connected to mechanisms powered by wound springs, much like the mainsprings in a clock. When released, the springs turned the wheels and moved the cart forward without a horse or human pushing it.

The cart was probably intended for theatrical or ceremonial use rather than transportation. One important feature was its programmable steering: small wooden pegs could be arranged to determine how the front wheels turned. This made the machine an early example of mechanical automation.

The cart is sometimes called Leonardo’s robot, although it was a vehicle rather than a humanoid machine. Its original construction details are incomplete, so modern builders have produced several interpretations. Reconstructions demonstrate that the design can move, but they do not prove that Leonardo built a fully working version himself.