What Leonardo da Vinci invention used a wound spring to move automatically without a visible driver?

Leonardo da Vinci’s self-propelled cart used wound springs to move automatically without a visible driver.

The cart was designed in the late 15th century and is often described as an early programmable machine or ancestor of the automobile. Two symmetrical springs stored energy, while a system of gears transferred that energy to the wheels. Steering could be set in advance through adjustable components, allowing the cart to follow a predetermined route rather than being continuously controlled by a rider.

Leonardo may have intended the device for theatrical performances, court celebrations, or ceremonial appearances. It was not a motor car in the modern sense: it carried no internal-combustion engine and had only limited stored energy. Reconstructions have shown that the basic mechanism can operate. The machine is also sometimes confused with Leonardo’s later mechanical lion, but the cart and the lion were separate designs.