It’s an effort from Nandivastu to explore the origin of vastu . It is the world where lord Vishnu rule. We have got a huge resemblance when we correlate Lord Vishnu image on vastu directions.
Lord Vishnu four hands are related to four directions in vastu . Ishanya( NE), Agneya(SE), Nirutya/kubera (SW) and vayuvya(NW) .The snake in picture represents North pole and South pole.
Northeast hand holding Conch shell , Southwest hand holding Mace , Southeast hand holding Lotus flower and Northwest hand having Sudarshana chakra.
If we examine further we find
1. Conch shell is found at sea, so water at Northeast
2. Mace is the symbol prosperity so its Kubera corner and Mace is the weapon of Lord yama and that is the reason we give place in Nairutya corner to our ancestors.
3. The Lotus is the attribute of Sun and Fire God . Rigdveda 6.16.13 clearly states that Sage Atarvan churned agni from Lotus . So its Agneya corner
4. Sudarshana Chakra travels in air. So it is vayuvya
If we note the order of water , fire , wind and ether. It clearly states in our chakra system of body as seen in the below picture.
Water element always stays below ground level , so in general concept NE we keep water element like sump or bore . So Northeast signifies down
Next is Fire Element which comes just above water . So it is SE should be little upper than NE
Next comes Vayu. Which denotes NW is little upper than NE and SE
Next comes Ether which signifies SW should be upper than all three.
This is my effort to decode vastu in my point of view