What machine did Leonardo da Vinci design as a self-propelled cart powered by coiled springs?

Leonardo da Vinci designed a self-propelled cart powered by coiled springs.

The cart used two large, symmetric springs hidden beneath its body to store energy. Gears transferred that energy to the wheels, while a programmable steering mechanism could make the cart follow a set path. The design is often described as an early robot or mechanical automaton because it could move without being pushed by a person.

Leonardo drew the machine around 1478 to 1480, but no surviving evidence shows that he built it. In 2006, a team led by Mario Taddei constructed a working replica based on the drawings. A later reconstruction by the Leonardo3 research center was used in public demonstrations. The cart was not powered by an engine or steam; its motion came from stored mechanical energy in springs, making it an important example of Renaissance automation.