Leonardo da Vinci improved an anemometer, an instrument used to measure the force or speed of wind.
His design used a vertical board that moved in response to airflow. A graduated scale allowed an observer to estimate the wind's strength from the board's position. Leonardo's version is generally associated with measuring wind force rather than providing the precise numerical speed readings expected from modern instruments.
Leonardo studied wind for practical and scientific reasons, including flight, weather and the behavior of projectiles. His notebooks contain observations of air currents and attempts to represent natural forces mechanically.
The word anemometer comes from Aeolus, the Greek keeper of the winds. Modern anemometers commonly use cups, propellers, ultrasonic sensors or heated wires. Leonardo's design was an early attempt to turn an invisible natural force into a visible, calibrated measurement.