Śatapatha Brāhmaṇa ("of a hundred paths") 6.7.1.28

6.7.1.28

atha sarvasampat | catvāraḥ pādāścatvāryanūcyāni śikyaṃ ca rukbhapāśaśca yadu kiṃ ca rajjavyaṃ śikyaṃ tadanūkhāgnī rukbhastattrayodaśa trayodaśa māsāḥ saṃvatsaraḥ saṃvatsaro 'gniryāvānagniryāvatyasya mātrā tāvattadbhavati

Now the total correspondence,--four feet and four boards (of the seat), the netting, and the sling of the gold plate, or any other corded netting; after that the pan and fire, and the gold plate,--that makes thirteen;--thirteen months are a year, and the year is Agni: as great as Agni is, as great as is his measure, so great does this become.