Leonardo da Vinci designed an odometer with a wheel and a ball-dropping counter.
His device was intended to measure distance traveled. As the wheel turned, a geared mechanism advanced the counting system. At a set interval, the machine released a small ball into a container, allowing the operator to count the measured units after a journey.
Leonardo’s odometer belongs to a long tradition of distance-measuring instruments. Ancient engineers had already used related wheel-based mechanisms, but Leonardo’s drawing shows how gears could connect wheel rotation to a practical counting process.
An odometer is not a compass, which indicates direction, and it is not a pedometer, which counts a person’s steps. Modern vehicle odometers usually display distance electronically or through precision mechanical gearing. Leonardo’s proposal used direct contact with the ground and a visible physical count.