Shatapatha Brahmana 7.5.1.14

7.5.1.14

prādeśamātre bhavataḥ | prādeśamātro vai garbho viṣṇurannametadātmasammitamevāsminnetadannaṃ dadhāti yadu vā ātmasammitamannaṃ tadavati tanna hinasti yadbhūyo hinasti tadyatkanīyo na tadavati

They measure a span, for Vishnu, when an embryo, was a span long; and these (mortar and pestle) being food, he thus puts food into him (Agni-Vishnu) proportionate to his body. And indeed the food which is proportionate to the body satisfies, and does no harm; but that which is excessive does harm; and that which is too little does not satisfy.