Māṇḍūkya Upaniṣad. which contains only twelve mantras belongs to Atharva-Veda. Although the Upaniṣad looks very small in narration; its greatness lies in the brevity with which it extols the aspect of Brahman. Muktikopanṣad asserts that study of only this Upaniṣad is sufficient for any serious sādhaka to attain liberation - Ēkaṁ Māṇḍūkyam-ēva alaṁ mumukṣūṇām vimuktayē.
“Upaniṣadbrahmayogi” who has commented on the one hundred and eight Upaniṣad-s, called this Upaniṣad as Sarva Vedānta Sāriṣṭha (the essence of the entire Vedānta). Ādi Śankara has called this Upaniṣad (which includes the Kārakā-s of Gaudapāda” as Sarva Vedānta Sāra Sangraha, in his Bhāṣya.
Just like in any other Upaniṣad, the theme of this Upaniṣad also is the extolling of Brahman. But the methodology used in this text is extra ordinary. The main contents is the analysis of the three states experienced by all mortals, namely , Jāgṛt , Svapna and Suśupti (waking, dream and dreamless sleep states). Through this, the Upaniṣad establishes the highest state of Turīya which is the state of Brahman. This is the great contribution of this Upaniṣad.
Prof Shastriji was at his best when he spoke on Manūkya Upaniṣad. He himself used to mention that he had read this Upaniṣad more than one hundred times to understand and appreciate the extolling of Omkāra. Omkāra sādhana being one of his favourite talks, I felt that any serious sādhaka should get to know the intricacies of the Omkāra.
The states of existence of a man has already been introduced in the Avastha Traya Parīkṣa. However an elaborate explanation of the two stages especially dream and sleep in the lecture is worth reading. Some of the talks on Māndūkya Upaniṣad contain excellent hints for a Sādhaka.
Shastriji has chosen some śloka-s from Gauapāda Kārika-s which have immense value. I have taken out the important ones and have reproduced here for the reader to benefit from them.
I am sure the reader will get the best out of the suggestions from the master. — Editor