Upanishads

As is the human body so is the cosmic body, As is the human mind so is the cosmic mind, As is the microcosm so is the macrocosm, As is the atom so is the universe. – from the Upanishads

Sankara held that reality is ultimately one and that the apparent plurality of the individual selves and entities of empirical existence is illusory: what seems to be an individual self, jivatma or atman, is in fact not essentially different from the one Self (Brahman), just as the space contained in an individual jug or pitcher is not different from space as a whole.