Śatapatha Brāhmaṇa ("of a hundred paths") 3.4.4.26

3.4.4.26

athāto vratopasadāmeva | paraurvīrvā anyā upasadaḥ paro 'hvīranyāḥ sa yāsāmekam prathamāhaṃ dogdhyatha dvāvatha trīṃstāḥ paraurvīratha yāsāṃ trīnprathamāhaṃ dogdhyatha dvāvathaikaṃ tāḥ paro 'hvīryā vai paro 'hvīstāḥ paraurvīryāḥ paraurvīstāḥ paro 'hvīḥ

Now then of the fast-homages. Some Upasads get wider and wider, others narrower and narrower: those at which he milks out one (teat) on the first day, then two, and then three, are those that get wider and wider; and those at which he milks out three on the first day, then two, and then one, are those that get narrower and narrower. Those getting narrower and narrower are (as good as) those getting wider and wider; and those getting wider and wider are (as good as) those getting narrower and narrower.