The Vastu Purusha Mandala, explained

Classical texts such as the Mayamata and the Mānasāra describe laying a square grid over the site before any wall is drawn. The 9×9 version — the Paramaśāyika mandala of 81 padas — is the one most used for homes.

Lying on that grid is the Vastu Purusha (वास्तु पुरुष): head in the north-east (ईशान), feet in the south-west (नैऋत्य). The image is a planning device — it gives every part of the plot a name and a role.

The Bṛhat Saṃhitā (ch. 53) lists the deities assigned to each pada: 32 around the boundary, the rest towards the centre, with Brahmā at the heart. Entrances are judged by which boundary pada they fall on.

The texts ask that the central zone stay free of heavy walls and pillars. In practice this produces the courtyard plan found across India — which, as our article on courtyards shows, also helps light and air move through the house.