By Concentration your mental matter does not acquire any form, but adopts only one form.
Concentration is made in two ways: one is objective and other subjective. One, as expression of the will, acts on a sense or determined form; other, as state of abstract mental consciousness, is over all senses.
First exercise: During hours of the morning, on an isolated and calm place, the student should be seated, straight his body and his head, and the hands relaxed on his knees; slowly he shall vocalize some holy formula or a constructive words that he prefers, imagining a golden yellow color all around him.
Contemplation is the definitive step of the soul from Asceticism to Mysticism.
It is called Secret Science of God and Divine Gift because at this point of spiritual development, the soul is directly enlightened by the Masters; that is why some believe and state that it is a gift, a grace of certain privileged souls, but not of all, and even the most advanced souls cannot intend to reach it.
Contemplation can be Shadowy or Illuminative. In fact, these divisions are arbitrary because these two states cannot be accurately determined. The soul becomes rather contemplative and remains absorbed by this holy exercise for a longer and longer time.
The soul becomes God in the Union. The soul remains as if deified; very subtle veils around the Superior Mind, which are the loftiest part of a being, disappear temporarily during the act of Supreme Realization, as if the Spirit absorbed and transformed entirely the soul.
Every rule aiming at achieving the Divine Union has its exception.
Certain souls never knew Meditation and others ignored Concentration but reached a perfect Union with God. Any indiscriminate imposition of these rules on everybody is to ignore that every soul is a separate world and needs its own rules and an especial development to reach the goal.