Weideman's stilliard, 1750-1800.
© Science Museum / Science & Society Picture Library
This device is a thick strip of steel bent into an approximate circle. A steel pointer is attached to one end of the circle and pases through a slot in the other in such a way that if a heavy weight is suspended the ends are drawn apart and the pointer moves over a bras scale on the other side of the circle. The bras scale is marked on both sides: one side is in pounds, the other is in degrees. The scales are extremely crude.