Śatapatha Brāhmaṇa ("of a hundred paths") 1.1.2.9

1.1.2.9

tasya vā etasyānasaḥ | agnireva dhūragnirhi vai dhūratha ya enadvahantyagnidagdhamivaiṣāṃ vaham bhavatyatha yajjaghanena kastambhīm pra ugaṃ vedirevāsya sā nīḍa eva havirdhānam

(Like) fire, verily, is the yoke of that very cart; for the yoke is indeed (like) fire: hence the shoulder of those (oxen) that draw this (cart) becomes as if burnt by fire. The middle part of the pole behind the prop represents, as it were, its (the cart's) altar; and the enclosed space of the cart (which contains the rice) constitutes its havirdhânam (receptacle of the sacrificial food).