What transport machine did Leonardo da Vinci design with a spring-powered mechanism and three wheels?

Leonardo da Vinci designed a self-propelled cart powered by coiled springs and guided by a programmable steering mechanism.

The cart appears in a drawing from the late 15th century and is often presented as an ancestor of the automobile. Two large rear wheels supported the vehicle, while a smaller front wheel helped with steering. Wound springs stored energy, and a system of gears transferred that energy to the wheels. The steering could reportedly be set in advance, allowing the cart to follow a predetermined route.

Because the original drawing is incomplete and the machine was not preserved, details of its construction remain debated. A modern reconstruction built for a 2006 exhibition demonstrated that the concept could move, although it was not a practical road vehicle. It used stored mechanical energy rather than an engine.