Of the first Normal Experiences, it hath been said:

'By retaining [or storing] in the psychic-centres the vital-force,
Something akin to heat is produced at first;
Secondly, blissfulness is experienced;
Thirdly, the mind assumeth its natural state;
Then the forming of thoughts ceaseth automatically,
And phenomena, appearing like smoke, mirage, and fireflies,
And something resembling the light of dawn,
And something resembling a cloudless sky are seen.'

Comments upon this quotation now follow.

The expiration being delayed by conscious effort, the psychic-force is retained in its own place [i.e. the psychic-centres]; and this process is called 'Retention.'

In virtue of the 'Retention' the number of breathings is reduced. This is called 'Retention of the Motion' [of the breath].

The shortening of the expiration is called 'Retention of the Length.'

The lessening of the force of the expiration is called 'Retention of the Force.'

The knowing of the colour of the breath is called 'Retention of the Colour.'

The absorbing of the power of the different elements is called 'Retention of the Power.'

The vital-force being retained thus, the waves of the Psychic-Heat and made stable.

Thereupon, the mind and the vital-force being tranquillized [or made to assume their natural condition of primordial quiesence], heat is produced.

That openeth out the apertures of the psychic-nerves, into which the psychic-force leadeth the 'moon-fluid' [tigle: male generative fluid, semen] and as a result there ariseth pain in the psychic-nerves.

Then seminal pain ariseth.

Then dawneth the experiencing of the conditions of existence in each of the Six Lokas [states of being]; and this, which cometh of the first stage of the transmuting of the seminal fluid, is called 'The Time of Pain,' or 'The Time of Warmth.'

Then, the atrophied psychic-nerves becoming rejuvenated by the psychic-force and by the seminal fluid, which continueth to increase and ripen [in its transmuted condition], one experienceth innumerable conditions of blissfulness of an inexhaustible sort. This is called 'The Second Stage,' or 'The Time of Blissfulness.'

Then, the mind being attuned by this internal bliss, one looketh upon all external nature with joyfulness. This is called 'The Experiencing of Bliss.'

The poison of the unceasing current of thought-formation is thereby neutralized and the mind attaineth its natural condition, the True State of Abiding Quiesence, or the tranquil state of Samadhi. This is called 'The Third Stage' or 'The State of Non-cognition' [of the phenomena of the external world], the third degree of proficiency reached in the training.

The state of quiesence thus realized is not a state devoid of all sensuous experiences; for phenomena appearing like smoke, and mirage, and fire-flies, and dull light, like that of a lamp, or the glimmer of twilight, and a cloudless sky, adn other phenomena, too numerous to be enumerated, illumine it in a supernormal manner.

During this third stage of the transmuting of the seminal fluid, the yogin [adept] who is experiencing it should not ignore any of the signs or omens which may thus phenomenally appear. Nor should he seek after those which do not appear, but he should keep on producing the Executive Psychic-Heat in the normal way.

The vital-force becoming effacious, the yogin becometh immune from diseases, aging, and other ordinary causes of physical deterioration; and he acquireth the fivefold supernormal knowledge of the inexhaustible sort, and innumerable other virtues.

Excerpted from Tibetan Yoga and Secret Doctrines, Bk. III, The Path of Knowledge, The Yoga of the Six Doctrines, The Doctrine of the Psychic Heat, Edited by W. Y. Evans-Wentz (1935).