What automatic device did Leonardo da Vinci design to roast meat evenly?

Leonardo da Vinci designed a roasting jack to turn meat automatically while it cooked.

A roasting jack is a mechanism that rotates a spit over a fire. Leonardo’s design used the movement of heated air and mechanical gearing to keep the spit turning, reducing the need for a person to rotate it by hand. Even rotation helped expose the meat more evenly to the heat.

The device demonstrates Leonardo’s interest in using natural forces to power useful household mechanisms. Hot air rising from a fire could drive a turbine-like element, which transferred motion through gears to the roasting spit.

A roasting jack is not a clock, although both can use gears and controlled motion. It is also not an oven: the jack rotates the food, while the fire or oven supplies the heat.