Shatapatha Brahmana 6.5.2.10

6.5.2.10

sa yadyekaḥ paśuḥ syāt | ekaprādeśāṃ kuryādatha yadi pañca paśavaḥ syuḥ pañcaprādeśāṃ kuryādiṣumātrīṃ vā vīryaṃ vā iṣuvīryaṃsammitaiva tadbhavati pañcaprādeśā ha sma tveva pureṣurbhavati

If there be one victim, let him make it (the pan) one span wide; and if there be five victims, let him make it five spans wide, or an arrow's width; for the arrow means strength: he thus makes it to be composed of strength. But, indeed, an arrow formerly used to be five spans long.