Stimpmeter
A device used to measure how fast a green is running, expressed in feet the ball rolls when released from a set height.
Invented in 1935 by Edward Stimpson, a former Harvard golf captain who watched Gene Sarazen's putt roll off a green at the 1935 U.S. Open and wanted actual proof the greens were too fast. His original wooden device sat unused for decades until the USGA redesigned it in aluminum and adopted it officially at the 1976 U.S. Open.