Skandapurana 6.3.220.29

6.3.220.29

anyathā hi kuruśreṣṭha devayonirasau vibhuḥ .
kuśāgreṇāpi vibudhairna spraṣṭavyo mahārṇavaḥ .. 220.29 ..

Otherwise, O best of the Kurus, this all-pervading [ocean] is of divine origin; / the great ocean is not to be touched by wise men even with the tip of a kuśa grass.