Shatapatha Brahmana 13.6.1.6

13.6.1.6

yadvevaikādaśinā bhavanti ekādaśinī vā idaṃ sarvam prajāpatirhyekādaśinī sarvaṃ hi prajāpatiḥ sarvam puruṣamedhaḥ sarvasyāptyai sarvasyāvaruddhyai

And, again, as to why there are (the victims) of the set of eleven (stakes): it is for the sake of his obtaining and securing everything, for the set of eleven (stakes) is everything, since the set of eleven (stakes) is Pragâpati, and Pragâpati is everything, and the Purushamedha is everything.