Shatapatha Brahmana 10.3.1.3

10.3.1.3

cakṣuruṣṇigiti tadya eva cakṣuṣo mahimā yadvīryaṃ tadetatsahasraṃ cakṣuṣa evaitadvīryaṃ yaddhyasya cinvataścakṣurutkrāmettata evaiṣo'gnirna cīyetaitenaivāsya rūpeṇa sahasrameṣa uṣṇihaḥ saṃcito bhavati

'The Ushnih is the eye,'--thus, whatever power, whatever vigour there is in the eye that is this one thousand; and to the eye, indeed, this vigour belongs, for were the eye-sight of him who builds it to pass away, this fire-altar, assuredly, would not be built: by this its form that (altar) becomes built (so as to contain) a thousand Ushnihs.