The Ribhu Gita (Ch. 5, v.39)

 With all objective knowledge banished, with no trace of thought or nescience, with all the three states of waking, dream and sleep wiped out, with all thought of death and birth abolished, and ever established in the spontaneous blissful state of brahman-Self the condition of the Videha-Mukta cannot be conceived, and much less expressed in words.