Śatapatha Brāhmaṇa ("of a hundred paths") 10.4.3.20

10.4.3.20

atha yā lokampṛṇāḥ muhurtalokāstā muhūrtānāmeva sāptiḥ kriyate muhūrtānām pratimā tā daśa ca sahasrāṇyaṣṭau ca śatāni bhavantyetāvanto hi saṃvatsarasya muhūrtāstāsāmekavih+śatiṃ gārhapatya upadadhāti dvābhyāṃ nāśītiṃ dhiṣṇyeṣvāhavanīya itarā etāvanti vai saṃvatsarasya rūpāṇi tānyasyātrāptānyupahitāni bhavanti

And as to the Lokamprinâ (space-filling bricks), supplying the place of muhûrtas (hours), they are made the (means) of gaining the muhûrtas, they are the counterpart of the muhûrtas: there are ten thousand and eight hundred of them, for so many muhûrtas there are in the year. Of these, he lays down twenty-one in the Gârhapatya (altar), seventy-eight in the Dhishnya-hearths, and the others in the Âhavanîya. So many, indeed, are the (different) forms of the year: it is these that are here secured for him (Pragâpati, the Year), and are put on him.