Leonardo da Vinci is credited with designing a hygrometer to measure humidity.
A hygrometer measures the moisture content of air. Leonardo’s early concept used a material that changed weight when it absorbed moisture, allowing differences in atmospheric dampness to be observed or measured.
The design belongs to Leonardo’s broader investigations of air, weather, and physical change. His notebooks frequently connect practical instruments with natural philosophy, and humidity was relevant to understanding clouds, storms, and the behavior of materials.
Leonardo’s device should not be confused with an anemometer, which measures wind speed, or a barometer, which measures atmospheric pressure. Later hygrometers used hair, paper, or chemical substances, and modern instruments commonly use electronic sensors. Leonardo’s contribution was an early attempt to quantify atmospheric moisture.