Vaastu Purusha because the legend in Matsya Puran goes was born out of the sweat of Lord Shiva whereas fighting and killing a giant referred to as “Andhakasur” and is lying down on the entire Earth with his head at the North East and feet at South West points of Earth.
Brahma, the creator of the universe and other Devas to appease his unsatisfied hunger, gave him a boon that whoever constructs building on Earth shall offer Pooja to him and make offerings if they need to enjoy health, wealth, wisdom and prosperity in their new buildings. this is how Vaastu Pooja came to be performed before beginning construction of any building.
As per to holy book of Hindu Vedic, there’s a ruling deity of God for every major activity like Brahma being the creator of this universe, whereas Lord Hindu deity being the giver of everything, Vaayu being God of Winds, Kuber God of Wealth, God of Rains Neptune or Varun, The governing deity for construction of buildings is Vastu Purusha . He’s considered to be in each and every plot of land whether or not big or small or conferring good or bad. According to the position or postures, there are three types of Vastu Purusha That he takes or makes.