Salinon

The salinon (meaning 'salt-cellar' in Greek) is a geometrical figure that consists of four semicircles.

It was first introduced in the Book of Lemmas, a work attributed to Archimedes.

[1] Let A, D, E, and B be four points on a line in the plane, in that order, with AD = EB.

Draw semicircles above line AB with diameters AB, AD, and EB, and another semicircle below with diameter DE.

is the radius of the small central semicircle, then the area of the salinon is:[4]

Should points D and E converge with O, it would form an arbelos, another one of Archimedes' creations, with symmetry along the y-axis.