Fortunatus X

The image here is the front of a postcard that was my contribution to the G4GX gift exchange. The text on the back of the card read:

Fortunatus X is a tribute to Martin Gardner designed for Gathering for Gardner X. This mathematical fiber arts piece is a variation on Fortunatus’s Purse, a curiosity described by Lewis Carroll in Sylvie and Bruno Concluded.

The original purse is a non-orientable surface (the real projective plane) sewn out of three square handkerchiefs. Since its outside and its inside are identical, the purse contains all the wealth of the world.

Fortunatus X replaces the cloth squares of the purse with three quilted X’s. While the purse passes through itself along one of its sewn edges, Fortunatus X twists in a more symmetric way, so that one arm of each X passes through a space between the other two X’s.

Fortunatus X was designed, executed, and photographed by Susan Goldstine, Associate Professor of Mathematics at St. Mary’s College of Maryland. Prof. Goldstine also wrote the chapter on Fortunatus’s Purse in Making Mathematics with Needlework: Ten Papers and Ten Projects, edited by sarah-marie belcastro and Carolyn Yackel.