Depictions of the "Endless Knot" symbol of Asian cultures (in some versions this is a symbol of Buddhism). In the series below, the knots have a number of crossings which is always the square of an odd number (but two of these crossings are not structurally significant).
Simplest form with 9 crossings, 7 of which are structurally significant (i.e. a 7_4 knot). Photograph of Susan Williams' medallion [1].
Abstract geometric version of preceding.
Form with 25 crossings, 23 of which are structurally significant.
Form with 49 crossings, 47 of which are structurally significant. Photograph of ca. 400 year old Chinese lacquerware dish.
Abstract geometric version of preceding.
Form with 81 crossings 79 of which are structurally significant.