Leonardo da Vinci’s anemometer was a device intended to measure wind speed with a swinging plate.
Around 1488, Leonardo designed a flat plate mounted so wind could push it upward. A graduated scale beside the plate would indicate how strongly the wind was blowing. The instrument did not directly display modern units such as metres per second, but it offered a repeatable way to compare wind strength.
Leonardo developed the idea while studying flight and atmospheric motion. His notebooks connect wind measurement with the performance of flying machines, showing that he understood the need for observations rather than guesses. The design is often described as an early plate anemometer.
Modern anemometers commonly use cups, propellers or ultrasonic sensors. A barometer measures air pressure, a thermometer measures temperature and a hygrometer measures humidity, so those instruments answer different questions.