In Optics, Claudius Ptolemy presents several experiments to verify the degree to which varyingly shaped surfaces separating two different transparent materials, modify the perception of an object viewed through them. Ptolemy had three containers made of perfectly transparent glass, so as to examine, in order, the action of a flat surface, a convex cylindrical surface, and a concave cylindrical surface (Optics , V, 67). After introducing a graduated straight-edge into each container, Ptolemy filled them with water and then, after emptying them, immerged them in water. The straight-edge always appeared to have an aspect different from natural: larger, smaller, or varyingly deformed.

In the reconstruction of these experiments, three glass containers with surfaces corresponding to Ptolemy's description are filled with water; three other containers, thoroughly similar to the former but left empty, are immersed in water. The containers are placed in front of a regular field of stars that occupies the position Ptolemy originally assigned to the graduated straight-edge. It thus becomes possible to verify the qualitative results that Ptolemy described for the container with the smooth face, as well as for the container with the convex cylindrical face (Optics, V, 68-86). The results he obtained for the third container with a concave cylindrical surface have been lost, along with the final part of Optics.

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