Leonardo da Vinci sketched an anemometer to show changes in wind speed.
His design used a light, movable plate attached to a vertical support. Wind pushed the plate upward, and markings could indicate the strength of the airflow. The instrument was intended to compare wind force rather than provide the precise digital speed readings produced by modern devices.
Leonardo’s interest in wind measurement was connected to his investigations of flight, air currents, and the behavior of moving fluids. A reliable way to observe wind was useful when thinking about flying machines and the performance of sails or wings.
An anemometer measures wind speed, while a wind vane measures wind direction. Those instruments are often confused because weather stations commonly place them together. Leonardo’s design was not the cup anemometer now familiar from weather stations; that later form was developed by John Thomas Romney Robinson in 1846. Leonardo’s sketch is instead an early mechanical attempt to make invisible airflow visible and comparable.