What vehicle did Leonardo da Vinci design to move without a visible external power source?

Leonardo da Vinci designed a self-propelled cart that could move through the stored energy of wound springs.

The cart appears in drawings from the late fifteenth century. Its mechanism used coiled springs inside drums to provide power, while programmable blocks on the axles helped determine the vehicle’s path. Because the springs were hidden within the body, the cart could appear to move without a visible external driver or animal.

Calling it a robotic vehicle can be useful, but “self-propelled cart” is the clearest description of the design itself. It was not powered by steam, electricity, or an internal-combustion engine. The cart also was not autonomous in the modern digital sense; its motion depended on mechanical settings established before operation.

A reconstruction built for a 2006 television program showed that the mechanism could work when interpreted carefully. The cart is significant because it combines stored mechanical energy, gearing, and programmed movement—ideas that anticipate later clockwork automata and mechanical control systems.