What Leonardo da Vinci invention is often described as a self-propelled cart?

Leonardo da Vinci’s self-propelled cart was a spring-powered vehicle designed to move without a person pushing it.

Leonardo sketched the cart around 1478–1480. Its concealed coiled springs supplied power, while a system of gears transmitted that power to the wheels. The design also included programmable steering features, allowing the cart to follow a predetermined route rather than simply travel in a straight line.

The cart is sometimes called an early automobile, but that comparison needs care. It was not powered by an engine or intended for ordinary road transport. Historians generally interpret it as a theatrical or ceremonial machine, perhaps built to surprise spectators at court events.

A full-scale reconstruction was made in 2006 by experts at the Museo Nazionale della Scienza e della Tecnologia in Milan. The reconstruction worked, supporting the practicality of Leonardo’s mechanical principles, although the original machine has not survived.