Verse 18

असदाभास एवात्मा अनन्तो भरिताकृतिः ।स्थितः सदैवैकघनो महाशैल इवात्मनि

In plain words

The Self, appearing indeed as though non-existent, infinite, its form utterly full, stands forever as a single dense mass, like a great mountain, within itself.