Someone commented on an article showing that a California court has allowed yoga to be taught in the public schools:
He wrote that he taught Transcendental Meditation (TM) for 10 years, he practices yoga, has been an orthodox rabbi for 20 years, and that there is no idolatry in them, nor is there any contradiction with them and Torah. He added that the only rabbis who are speaking out against these things have no experience with them so they do not know what they are talking about.
Transcendental Meditation is a mantra meditation system. Mantra meditation is the repetition of a word (the mantra), a name, or a meaningless sound, over and over again. The purpose is to detach from all other mental input. This invariably leads away from the Jewish goal.
TM was made popular in West in the 1960's by an Indian guru who had a large following. As its name indicates, it goal is to transcend worldly consciousness and to attain "Universal Consciousness." Yet, not a single one of the hundreds of thousands of devotees has ever claimed to have obtained this consciousness, not even after 20 or more years of daily meditation. They sell "secret" mantras to their initiates. Many of the mantras are names of idols, and many others are nonsensical words invented just to be sold. But the main problem is not just that the mantras are foolish.
This type of meditation is called entirely passive because the mind focuses on a subject that you are not interested in learning about. This pacifies mental activity. Typical subjects for this type of meditation are a word, a sound, a flame, a crystal ball, and such.
To the opposite of this, if the subject is something that you do want to learn more about, then the mind becomes actively engaged, and this is called active meditation. Such subjects as; Where is G-d? What is my soul? Where is Place? are active subjects.
In both systems the exercise is the same. As soon as you realize that you have drifted away from the subject, return your awareness back onto the subject again, and again.
The main problem with TM, besides the very real association with Hindu idolatry, is that its primary result is detachment. Although this brings some positive results, such as calming the blood pressure, detachment is not a proper Jewish goal.
The goal of Jewish meditation, as with all Jewish practices, has to be to elevate the world, not to forsake it.
In order to safely reap the various benefits of passive meditation, one can combine the two techniques. For instance, gently focus on your breath as it moves in and out of your nose. This is an entirely passive technique. But then, after every few cycles of watching your breath move in and out, recall that, "Just as did Hashem breathe the breath of life into Adam, so is He breathing my breath in and out of me." This brings an active element into the passive technique as you try to become acutely aware of G-d's Presence and hand in your life.
The benefit of active meditation is increased understanding of the chosen subject. Its goal is to elevate the meditators' spiritual awareness. This cannot be accomplished by simply repeating a senseless word over and over again.
As to his statement that yoga has no connection to idolatry, last year the New York Tax Authority agreed with the petitioning yoga studios that they should be exempt from paying taxes since they are teaching a mostly spiritual practice and not just a physical exercise system.