The Vastu Purusha Mandala serves as a ground plan for Hindu temples. There are two fundamental types: one with 8 x 8 = 64 squares. This is also the number of squares in a chess board and a checkerboard and number of hexagrams in the I Ching. The second type has 9 x 9 = 81 squares. this is also the number of scales in the ideal dragon as described in the I Ching.
This is discussed in Lecture 13A: Patterns Order