The harmonograph is a machine for creating mathematical drawings. Begin by putting a piece of paper under the middle or one end of the bar. Hold the paper down with a couple of magnets. Start the harmonograph moving without a pen. After it has settled into a regular motion, gently add the pen (or multiple pens).

Pay attention to the number of people waiting in deciding how much time to give each participant. Visitors can take home the pictures that they make.

The harmonograph has multiple motions that combine together. Sliding the weights and turning the knobs change the natural frequency of the rotational motion, creating different pictures. Participants may wish to try to determine the effect of making these sorts of changes. Participants may also wish to try giving the harmonograph a slight tap after it has settled into a regular motion, which may result in new patterns.