l—It results in egoic contact and alignment.
2—It brings about a state of equilibrium.
3—It stabilises vibration.
4—It assists in a transference of polarisation.
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June 3, 1920.

Four things meditation does:
l—It enables a man to contact the Ego and to align the three lower bodies.
2—It puts a man into an attitude of equilibrium, neither utterly receptive and negative, nor utterly positive, but at the point of balance. Thus is afforded opportunity to the Ego, and later to the Master, to disturb that equilibrium and tune the quiescent vibration to a higher note than heretofore.
3—It stabilises the lower vibrations on the subplanes of the emotional and mental planes.It commences the work of attuning the self to the vibration of the third subplane on each of the three lower planes, until that subplane is dominated. The second subplane is then the next to be synchronised.
A man reaches the point of personality attainment in this cycle when he has the capacity to vibrate and move consciously on the fourth subplane.We might term the fourth subplane on the physical, emotional and mental planes (when dominated, aligned and functioning simultaneously in the same incarnation) the plane of perfected personality in the concrete sense of the word, and from the lower vision.That particular incarnation will be one in which the man achieves the fullest expression of his lower self,—physically perfect, emotionally vibrant, and mentally colossal.  Then succeeding that, begins the transference to a higher vibration, the keying up to the Higher Self, and the attuning of the Personality, or the major third, to the dominant fifth of the Ego.
4—It assists in the transference of the polarisation from one of the permanent atoms of the Personality into the corresponding atom in the spiritual Triad....

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Hence may easily be seen the essential nature of Meditation and its wise, diligent and serious following.
Early in experience, after the attainment of the highest the lower nature has to offer, man begins to meditate. Disorderly at first are his attempts, and sometimes several incarnations may go by in which the Higher self only forces the man to think and seriously to meditate at rare and separated intervals. More frequently come the occasions of withdrawing within, until there arises for the man several lives given to mystic meditation and aspiration, culminating usually in a life given entirely to it.It marks the point of the highest emotional aspiration, apart from the scientific application of the law, via the mental body. These laws are those governing the true occult meditation.
(A.A.Bailey, Letters on Occult Meditation).

Some Practical Hints.....  Let me give a few preliminary hints:—
The aspirant seeks daily a quiet spot where he can be free from interference and interruption.  If wise, he will always seek the same spot, for he will there build up a shell around it that will serve as a protection and make the desired higher contact more easy.  The matter of that spot, the matter of what you might term the surrounding space, becomes then attuned to a certain vibration (the man's own highest vibration, reached in consecutive meditations) which makes it easier for him each time to start at his highest and so eliminate a long preliminary keying up.
The aspirant composes himself to a position in which he can be unconscious of his physical body.  No hard and fast rules can be laid down as the physical vehicle itself has here to be considered,—it may be handicapped in some way, stiff or crippled.  Ease of posture is to be aimed at, coupled with alertness and attention.  Slothfulness and laxness lead a man nowhere.  The position most suitable for the average is cross-legged upon the ground, sitting against something that affords support to the spine.  In intensest meditation or when the aspirant is very proficient and the centres rapidly awakening (perhaps even the inner fire pulsating at the base of the spine) [Page 62] the back should be erect without support.  The head should not be thrown back as tension is to be avoided, but it should be held level, or with the chin slightly dropped.  When this is done, that tenseness that is the characteristic of so many will be gone and the lower vehicle will be relaxed.  The eyes should be closed and the hands folded in the lap.
Then let the aspirant note if his breathing is regular, steady and uniform.  Should this be so, let him then relax his entire person, holding the mind positive and the physical vehicle supple and responsive.
Then let him visualize his three bodies, and having decided whether his meditation shall be in the head or within the heart (I will later take up this point) let him withdraw his consciousness there and focus himself in one or other of the centres.  In so doing let him deliberately realise that he is a Son of God, returning to the Father; that he is God Himself, seeking to find the God-consciousness which is His; that he is a creator, seeking to create; that he is the lower aspect of Deity seeking alignment with the higher.  Then let him three times intone the sacred Word, breathing it forth gently the first time and thereby affecting the mental vehicle; more loudly the second time, thereby stabilising the emotional vehicle; and in a still louder tone the final time, acting then upon the physical vehicle.  The effect upon each body will be threefold.  If correctly chanted with the centre of consciousness steadily held within whichever centre has been chosen, the effect will be as follows:

On Mental Levels:
a—The contacting of the head centre, causing it to vibrate.  The stilling of the lower mind.
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b—Linking up with the Ego to a more or less degree, but always to some extent through the permanent atom.
c—The driving out of coarse particles and the building in of finer.

On Emotional Levels:
a—The definite stabilisation of the emotional body through the permanent atom, and the contacting and setting in motion of the heart centre.
b—The driving out of coarse matter and the rendering of the emotional or desire body more colourless, so that it will be a true reflector of the higher.
c—It causes a sudden rush of feeling from the atomic levels of the emotional plane to the intuitional plane, via the atomic channel that exists between the two.  It sweeps upward and clarifies the channel.

On the Physical Planes:
a—Here the effect is very similar, but the primary effect is on the etheric body; it stimulates the divine flow.
b—It passes beyond the periphery of the body and creates a shell that serves as a protection.  It drives away discordant factors in the near environment.
(A.A.Bailey, Letters on Occult Meditation).