In a darkened room suspend a point of light on a thread from the ceiling; put a camera on the floor; give the source a swing; and open the shutter for a while. The result is a recording of the path of the luminous point.
A simple pendulum, as in a clock, would produce only a straight line, but if the bob can swing in all directions straight lines, circles, and ellipses can be the result:
A Lissajous suspension produces more interesting results. The pendulum has one length in one plane and a shorter one in a swing plane at right angles to it. The result is the family of Lissajous figures:
And, just for laughs:
