The Vastu Purusha Mandala
The square diagram on which a temple is laid out: 64 or 81 padas in concentric zones around the Brahmasthana.
The rules it illustrates
Find the cardinal points with a gnomon. Set a vertical rod at the centre of the levelled site, draw a circle round it, mark where the tip of its shadow crosses the circle before and after noon, and join the two marks: that line runs east–west.
The rule of the diagonal. The cord stretched along the diagonal of a rectangle produces as much area as the cords along its two sides together; use this to set out right angles and to make squares of any required area.
The site is a squared diagram. Divide the square site into a grid of equal squares (padas), most often 8 × 8 = 64 or 9 × 9 = 81, and place every part of the building according to the grid.
The being of the site. Imagine the vāstupuruṣa lying face down on the diagram with his head in the north-east and his feet in the south-west, held down by the gods who occupy the padas; do not place walls, pillars or doors on his vital points.
Concentric zones of sanctity. Read the diagram from the centre outward: Brahmā at the heart, then a ring of the gods, a ring of human concerns, and on the outside the lesser spirits; the holiest function goes at the centre and the most worldly at the edge.
The sanctum over the centre. Place the garbhagriha (the small dark chamber that houses the image) over the Brahmasthana, with its walls on the ring of the gods and its door on the axis, usually to the east.
Where it appears in the book
In the styles Buddhist India, Hindu Temple: Nagara (North Indian), Hindu Temple: Dravida (South Indian), Khmer.
In the chapters South and Southeast Asia, Reading the Treatises.