Śatapatha Brāhmaṇa ("of a hundred paths") 8.7.2.12

8.7.2.12

sa yasyāṃ sraktyām prathame upadadhāti | tato daśabhirdaśabhiḥ saṃcādayannetyā svayamātṛṇāyai sa tenaiva dakṣiṇāvṛjjaghanena svayamātṛṇāṃ saṃcādayannetyānūkyāyā atha punaretya tamavadhiṃ saṃcādayati

From the corner in which he lays down the first two (Lokamprinâs) he goes on filling up (the altar) by tens up to the Svayamâtrinnâ. In the same way he goes on filling it up from left to right behind the naturally-perforated one up to (the brick on) the cross-spine. He then fills it up whilst returning to that limit.