Leonardo da Vinci designed an anemometer, an instrument for observing wind direction and estimating wind strength.
Leonardo’s version used a lightweight plate or surface that could move in response to air. Its position could indicate the direction of the wind, while the amount of movement could provide an indication of its force. The device was useful in the context of Leonardo’s studies of flight, because wind conditions affect birds, gliders, and other aircraft.
An anemometer is not the same as a barometer. An anemometer measures wind speed or wind force, whereas a barometer measures atmospheric pressure. Modern cup, vane, propeller, and ultrasonic anemometers use more precise mechanisms, but they preserve the same basic goal of quantifying moving air.
Leonardo’s instrument was an observational device rather than a powered machine. Its significance comes from connecting weather measurement with practical engineering. His notebooks repeatedly treat wind as something that could be studied, recorded, and used in designing flying machines.