Leon Battista Alberti invented the first anemometer in 1450 A.D. His invention was a disk that was perpendicular to the direction of the wind, which measured wind speed.
The type of anemometer that is common today, the cup-shaped variety, was not invented until 1846 by John Thomas Romney Robinson. He used four cups and wheels on his anemometer. The design was improved again in 1926 by John Petterson, who simplified the design to 3 cups.
Today's anemometers measure wind speed, wind pressure and wind direction. Wind speed is calculated by counting the number of times the cups on the instrument turn. They help meteorologists analyze how weather works, which assists with weather predictions.