Shatapatha Brahmana 13.6.1.3

13.6.1.3

tā vā etāḥ catasro daśato bhavanti tadyadetāścatasro daśato bhavantyeṣāṃ caiva lokānāmāptye diśāṃ cemameva lokam prathamayā daśatāpnuvannantarikṣaṃ dvitīyayā divaṃ tṛtīyayā diśaścaturthyā tathaivaitadyajamāna imameva lokam prathamayā daśatāpnotyantarikṣaṃ dvitīyayā divaṃ tṛtīyayā diśaścaturthyaitāvadvā idaṃ sarvaṃ yāvādime ca lokā diśaśca sarvam puruṣamedhaḥ sarvasyāptyai s!rvasyāvaruddhyai

Now these (forty days) are four decades; and as to there being these four decades, it is for the obtainment of these worlds, as well as of the regions: by the first decade they obtained even this (terrestrial) world, by the second the air, by the third the sky, and by the fourth the regions (quarters); and in like manner does the Sacrificer, by the first decade, obtain even this (terrestrial) world, by the second the air, by the third the sky, and by the fourth the regions--and, indeed, as much as these worlds and the regions are, so much is all this (universe); and the Purushamedha is everything: thus it is for the sake of his obtaining and securing everything.