Leonardo da Vinci’s odometer was an invention for counting distance traveled by dropping a stone at regular intervals. His design connected wheel rotation to a mechanism that released one stone after the wheel had completed a set number of turns.
The device was intended for surveying and mapping. As the wheel rolled across the ground, its circumference provided a basis for estimating distance. A hopper or container collected the dropped stones, allowing the operator to count them after the journey. This made the instrument a mechanical distance recorder rather than a speedometer.
Leonardo’s odometer belongs to a long history of wheel-based measurement. The principle is straightforward: if the wheel’s circumference is known, each revolution represents a known distance. Slippage, uneven ground, and inaccurate wheel size could still introduce errors.
Modern vehicle odometers use gears, electronic sensors, or software, but they preserve the same basic relationship between movement and recorded distance. Leonardo’s design is sometimes mistaken for a device that measured speed; an odometer records distance, while a speedometer records speed.