Hymn to Siva - Verse 22-23

But Visnu, the source of the universe, heard this with wonder. Being permitted by lord Brahma, the creator of the worlds, the great Yogin Visnu entered the mouth of Brahma, out of curiosity. After entering he saw in the belly of Brahma, these eighteen continents, along with oceans, and mountains, the living beings beginning with Brahma and ending with a blade of grass, people of four castes and the eternal seven worlds.