Tractrix

The path of an object dragged by a string of fixed length whose other end moves along a straight line. Claude Perrault posed it in 1670 with a watch on its chain, the end of the chain drawn along the edge of a table. Turned about that line, it makes the pseudosphere.

x = t - tanh t, y = 1/cosh t

On mathcurve.com as Tractrice