“A topsail bellied out by the wind is not a catenoid surface, but in vertical section is everywhere a catenary curve; and Dürer shows beautiful catenary curves in the wrinkles under an old man’s eyes. A simple experiment is to invert a small funnel in a large one, wet them with soap solution, and draw them apart; the film which develops between them is a catenoid surface, set perpendicularly to the two funnels. On this and other geometrical illustrations of the fact that a soap-film sets itself at right angles to a solid boundary, see an elegant paper by Mary E. Sinclair, in Annals of Mathematics, 8 (1907).”

(D’Arcy Wentworth Thompson, On Growth and Form, p. 57, note 1.)