Śatapatha Brāhmaṇa ("of a hundred paths") 8.2.1.17

8.2.1.17

tadyadete atropadadhāti | saṃvatsara eṣo 'gnirima u lokāḥ saṃvatsarastasya yadūrdhvam pṛthivyā arvācīnamantarikṣāttadasyaiṣā dvitīyāṃ citistadvasya grīṣma ṛtustadyadete atropadadhāti

And as to why he lays down these two in this (layer):--this Agni (fire-altar) is the year, and the year is these worlds. Now that part of him which is above the earth and below the atmosphere, is this second layer; and that same part of him (Agni, the year,) is the summer season. And when he lays down those two in this (layer), he thereby restores to him (Agni) that part of his body which these two are: this is why he lays down these two (bricks) in this (layer).