Mandukya 7 Listen

Turīya is not that which is conscious of the internal (subjective) world, nor that which is conscious of the external (objective) world, nor that which is conscious of both, nor that which is a mass all sentiency, nor that which is simple consciousness, nor that which is insentient. (It is) unseen (by any sense organ), not related to anything, incomprehensible (by the mind), uninferable, unthinkable, indescribable, essentially of the nature of Consciousness constituting the Self alone, negation of all phenomena, the Peaceful, all Bliss and the Non-dual. This is what is known as the fourth (Turīya). This is the Ātman and it has to be realised.