ANSWER: The Vastu Purusha is said to be the spirit of the site with human male form and who lies on the site his head towards the east, his posture fitting exactly in a square. The square being the form recommende for most structures. It was easier to get the anthropometrically and aesthetically correct dimensions of rooms, doors windows and even the structural members like plinth and pillars. Even the interior planning was governed by the posture of the Vastu Purusha and the norms were said, which specified where and how the structure must be built, so that it does not injure the Vastu Purusha.