Watt's curve

Watt's curve, a figure-eight shaped curve formed by a mechanical linkage.

In mathematics, Watt's curve is a tricircular plane algebraic curve of degree six.

Watt's curve is a tricircular sextic.

Watt's curve is the zero set of the degree-six polynomial equation and has the lemniscate of Bernoulli as a special case.

Rather, it traces out Watt's curve, a lemniscate or figure eight shaped curve; when the lengths of its bars and its base are chosen to form a crossed square, it traces the lemniscate of Bernoulli.