Śatapatha Brāhmaṇa ("of a hundred paths") 13.8.4.11

13.8.4.11

athānagnicitaḥ etadeva bhūmijoṣaṇametatsamānam karma yadanyadagnikarmaṇaḥ kurvādāhitāgneḥ śarkarā ityu haika āhuryā evāmūragnyādheyaśarkarāstā etā iti na kuryādityeka īśvaro haitā anagnicitaṃ santaptoriti sa yathā kāmayeta tathā kuryāt

And in the case of one who has not built a fire-altar, there is the same mode of selecting the site (for the sepulchral mound) and the same performance save that of the fire-altar. 'Let him use pebbles (instead of bricks) in the case of one who keeps up a sacrificial fire,' say some, 'they are just what those pebbles used at the Agnyâdheya are.' 'Let him not use them,' say others; 'surely they would be liable to weigh heavily upon one who has not built a fire-altar.' Let him do as he pleases.