Pintograph

My new iPhone app PINTOGRAPH aptly describes how my back feels today! At work this weekend & I'm sure A&E will keep me busy!

A harmonograph is a mechanical apparatus that employs pendulums to create a geometric image. The drawings created typically are Lissajous curves, or related drawings of greater complexity. The devices, which began to appear in the mid-19th century and peaked in popularity in the 1890s, cannot be conclusively attributed to a single person, although Hugh Blackburn, a professor of mathematics at the University of Glasgow, is commonly believed to be the official inventor.

A particular type of harmonograph, a pintograph, is based on the relative motion of two rotating discs.