Śatapatha Brāhmaṇa ("of a hundred paths") 13.8.1.5

13.8.1.5

catuḥsrakti devāścāsurāścobhaye prājāpatyā dikṣvaspardhanta te devāasurāntsapatnānbhrātṛvyāndigbhyo'nudanta te'dikkāḥ parābhavaṃstasmādyā daivyaḥ prajāścatuḥsraktīni tāḥ śmaśānāni kurvate'tha yā āsuryaḥ prācyāstvadye tvatparimaṇḍalāni te'nudanta hyenāndigbhya ubhe diśāvantareṇa vidadhāti prācīṃ ca dakṣiṇāṃ caitasyāṃ ha diśi pitṛlokasya dvāraṃ dvāraivainam pitṛlokam prapādayati sraktibhirdikṣu pratitiṣṭhatītareṇātmanāvantaradikṣu tadenaṃ sarvāsu dikṣu pratiṣṭhāpayati

Four-cornered (is the sepulchral mound). Now the gods and the Asuras, both of them sprung from Pragâpati, were contending in the (four) regions (quarters). The gods drove out the Asuras, their rivals and enemies, from the regions, and, being regionless, they were overcome. Wherefore the people who are godly make their burial-places four-cornered, whilst those who are of the Asura nature, the Easterns and others, (make them) round, for they (the gods) drove them out from the regions. He arranges it so as to lie between the two regions, the eastern and the southern, for in that region assuredly is the door to the world of the Fathers: through the above he thus causes him to enter the world of the Fathers; and by means of the (four) corners he (the deceased) establishes himself in the regions, and by means of the other body (of the tomb) in the intermediate regions: he thus establishes him in all the regions.