What Leonardo da Vinci design used a four-wheeled platform powered by coiled springs?

Leonardo da Vinci’s four-wheeled spring-powered vehicle is known as the self-propelled cart.

Leonardo designed the cart around 1478–1480. Its two symmetrical springs stored energy and drove the wheels through gearing, allowing the vehicle to move without being pulled by an animal. A steering system could be set in advance, so the cart followed a predetermined route rather than responding to a driver in real time.

The machine is sometimes called an early automobile, but that description can mislead. It had no combustion engine, steering wheel, or modern braking system. It was closer to a programmable mechanical stage vehicle, probably intended for theatrical or ceremonial use. Leonardo’s surviving drawings are not a complete modern construction manual, so later builders have had to interpret some details.

The cart is especially significant because it combined stored mechanical energy, gearing, and automatic motion. In 2006, researchers in Florence built a working model based on the design, supporting the feasibility of its basic mechanism.