A device consisting of two coupled pendula, usually oscillating at right angles to each other, which are attached to a pen. The resulting motion can produce beautiful,
complicated curves which eventually terminate in a point as the motion of the pendula
is damped by friction. In the absence of friction (and for small displacements so
that the general pendulum equations of motion become simple
harmonic motion), the figures produced by a harmonograph would be Lissajous
curves.
