Leonardo da Vinci designed a hygrometer to estimate humidity by comparing material weights.
A hygrometer measures the moisture content of air. Leonardo’s early concept used materials that changed weight when they absorbed moisture, allowing differences to be observed or compared. This approach belonged to a broader Renaissance effort to make atmospheric conditions measurable rather than relying only on human sensation.
Leonardo’s hygrometer was an early design, not a modern electronic instrument. Later hygrometers used substances such as hair, which lengthens as humidity rises, while contemporary devices often use electronic sensors.
Humidity measurement mattered to Leonardo because he studied weather, water, air, and the behavior of materials. The device is therefore connected to his investigations of natural processes as well as to practical measurement.