The most powerful exercise in the world to develop clairvoyance is the so-called “retrospective exercise” in occultism.
The disciple, immersed in deep inner meditation, starts his practice as follows: he tries to remember in detail the last incidents of his life which occurred during the day; later, he will address the memories of the previous day; after, those of the day before that, and so on. So, he should apply his perception and his retrospective attention to the whole drama of his life. In the end, he will remember the last fifteen days, the last month, the month before that…, the last year, the year before that, etc., always in a retrospective way, like someone who is reviewing the reading of a book from the last page to the first one, without skipping any intermediate page.
It happens that when trying to remember the first seven years of ones infant life, the retrospective practice becomes more difficult. However, one has to accept that all incidents, all representations of that period of our childhood, are deposited in the bag of the subconscious, and the important task is to bring to the light of the Consciousness those memories from the bottom of that bag.
This is only possible in the act of surrendering to sleep. Every human being contacts the subconscious during the time of sleep. Well, as soon as he is asleep, the disciple will combine the retrospective exercise with sleep; and he will strive for remembering, we repeat, all incidents of his life until he was seven years old, always in a backwards way: he will review year by year, from the seventh to the first year, and later until the moment of his birth. He can be sure that memories will emerge little by little, after arduous efforts and numerous and tireless retrospective practices night by night.
Samael Aun Weor
Logos, Mantra, Theurgy, chapter 9