
There are seventeen possibilities, which were first classified by Eugraf Federov in 1881; but it appears that they were all known, and employed for decorative
purposes, by the ancient Egyptians. The most spectacular renderings of them are to be found in the Moorish decorations on the Alhambra. When one departs from these regular designs, which all have a
latticelike structure that is invariant after moving along vertical or horizontal directions, the number of possible designs grows dramatically. In fact, any one of the patterns can then be combined with
the others in an infinite number of different permutations.
Text from ‘The Artful Universe’ by John Barrow
