Śatapatha Brāhmaṇa ("of a hundred paths") 6.5.2.22

6.5.2.22

tā haike tisraḥ kurvanti | trayo vā ime lokā ime lokā ukhā iti vadanto 'tho anyo 'nyasyai prāyaścityai yadītarā bhetsyate 'thetarasyām bhariṣyāmo yadītarāthetarasyāmiti na tathā kuryādyo vā eṣa nidhiḥ prathamo 'yaṃ sa loko yaḥ pūrva uddhirantarikṣaṃ tadya uttaro dyauḥ sātha yadetaccaturthaṃ yajurdiśo haiva tadetāvadvā idaṃ sarva yāvadime ca lokā diśaśca sa yadatropāharedati tadrecayedyadu vai yajñe'tiriktaṃ kriyate yajamānasya taddviṣantam bhrātṛvyamabhyatiricyate yadu bhinnāyai prāyaścittiruttarasmiṃstadanvākhyāne

Now some make three (fire-pans), saying, 'Three (in number) are these worlds, and the fire-pans are these worlds;' and also for mutual expiation, thinking, 'If the one will break, we shall carry (Agni) in the other, and if the other (breaks), then in the other (or third).' Let him not do so; for that first bottom part is this world; and that first (lower) side-part is the air; and the upper one is the sky; and that fourth, the prayer, doubtless is the quarters; and just as much as these worlds and the quarters are, so much is this whole (universe). But were he to add anything thereto, he would make it to be redundant, and whatever redundant (act) is done in the sacrifice is left over for the Sacrificer's spiteful rival. And as to the expiation in case of the (fire-pan being) broken, that (will be told) in a subsequent chapter.