Śatapatha Brāhmaṇa ("of a hundred paths") 7.3.1.39

7.3.1.39

tadāhuḥ | kathamasyaitā ahorātraiḥ sampannā anyūnā anatiriktā upahitā bhavantītyanantāni vā ahorātrāṇyanantāḥ sikatā evamu hāsyaitā ahorātraiḥ sampannā anyūnā anatiriktā upahitā bhavantyatha kasmātsamudriyaṃ canda ityananto vai samudro 'nantāḥ sikatāstatsamudriyaṃ candaḥ

As to this they say, 'How does that (sand), put on by the days and nights, become complete (or perfect) for him, neither deficient, nor superabundant?' Well, endless are the days and nights, and endless is the sand: it is thus that, put on by the days and nights, it becomes complete for him, neither deficient, nor superabundant. 'And wherefrom (is obtained) the oceanic (Samudriya) metre?' The ocean is endless, and the sand is endless: that is the oceanic metre.