According to vastu, the vastu purusha is lying in a position where the head position is in the ishan corner (ishan cone), which is the north east direction, the legs in the niryathi corner (niryathi cone), which is the south west direction, the elbows in the vayu corner (vayu cone),which is in the north west direction, and knees in the agni corner (agni cone), which falls in the south east direction.
But the direction in which vastu purusha lies, changes every three months according to the rotation of the earth. In the months of September, October, November& December, the head position of vastu purusha will be in the eastern direction, the legs in the western direction and sight in the southern direction. The direction of lying changes to head in south direction, legs in the north direction and sight to the western direction, in the months of December (half), January, February, and March. During the months from mid- March, April, May & June, vastu purush lies with head to the west, legs to the east, and sight in the northern direction. In months from mid-June, July, August and September, the head of vastu purush changes to the northern side, legs to the southern side, and sight to the eastern direction.