Once a person dies, his/her post-death rites are to be performed at the hands of a priest as mentioned in the Scriptures. Finding a priest with the knowledge of post-death rites is difficult in most places. Under such circumstances, one should place the dead body on the pyre in such a manner that the feet of the dead body are towards the north. The reasons and science underlying such an act are explained below.
1. To facilitate the union of the individual with Shiv (God Principle)
North is the direction of Deity Som’s abode, that is it is the abode of Deity Shiv in Principle form. Hence, the distressing vibrations emitting from the region below the waist are disintegrated to a maximum extent instantly. This facilitates union of the individual with Shiv.
The dead body gets protected from the attacks of negative energies : The dead body placed on the pyre in a crematorium is cremated with the help of mantrāgni (Fire reinforced with the power of mantras). In this process, with the help of the energy of mantras, the rite is performed free from the attacks of negative energies.
Getting assistance in the formation of a protective sheath of Tēj-tattva (Absolute Fire Principle) around the dead body : The dead body is placed on a pyre with its feet facing the north, so that the mantra reinforced Tēj-tattva in the fire converges in a better way around the body in the form of a protective sheath.
Getting assistance in the disintegration of waves of putrefying gases under the control of Deity Som in the north direction : The presiding Deity of north direction is Som. It is a form of Shiv-tattva (God Principle) that plays an important role in union of the individual with Shiv. It is in this direction that the distressing vibrations emitting from the region below the waist are disintegrated to a maximum extent. Since this direction is very conducive for the union of the individual with Shiv in the final moments, only when keeping the deceased on a pyre, its legs are placed facing the north.
Receiving maximum protection from Bhulok (earth region) in the final moments and assistance for further momentum : Due to the Tēj-tattva in the mantrāgni, waves of inferior Deities and several other favourable Deities which are in the north direction, are awakened. Arrival akin to Pruthvī-tattva (Absolute Earth Principle) and Āpa-tattva (Absolute Water Principle) of these waves from the north direction provides maximum protection to the dead from Bhulok in the final moments and assists in getting further momentum.
2. To facilitate giving the custody of the deceased to Deities
During the Agnīsanskār (Ritual of offering the dead body to the fire), the deceased is supposed to be offered to the Agnīdēvatā (Deity of Fire). The Deities of worship always arrive from the north direction. The feet of an individual are symbolic of walking a path. The dead body is placed on the pyre with its feet facing the north so as to facilitate its going into the custody of the Deities.
Reference : Sanatan’s Holy Text, ‘Death and post-death rites’