Hilbert's 'Monkey Saddle' and Other Curiosities in the Equilibrium Problem of Three Point Particles on a Circle for Repulsive Power Law Forces | Journal of Dynamics and Differential Equations
Mathematical model, computer artwork. This model surface is known as a monkey saddle. - SuperStock
File:Monkey saddle.png - Wikipedia
multivariable calculus - What is a dog saddle? - Mathematics Stack Exchange