From: The World In Your Head by Steven Lehar

Fig. 6.7 (A) A hypothetical scheme for the representation of visual form in terms of orders of symmetry of its vertices about a center, indicated by the number below each figure. The forms themselves are reified from the abstracted configuration of vertices by a process analogous to inflating a bubble surface around a wire frame skeleton. (B) A first harmonic modifier stretches these shapes in one direction, whereas (C) a second harmonic modifier stretches them in two opposite directions. (D) More complex compound forms can be defined by a hierarchical code that expresses a central and peripheral symmetry. (E) An even more general code expresses different peripheral symmetries on each branch of the central symmetry.