From Chapter 9, Meta Modern Era by Shri Mataji Nirmala Devi
#16 Spiritual Awakening
In Gita there is no description of the Kundalini or of the awakening, though Shri Krishna, at the very outset, has said that a person should achieve the state of ‘sthitapragya’, which means the one who is balanced, through enlightenment, by divine knowledge. All this was a description but he did not talk about how it is brought about.
It was Shri Gyaneshwara who wrote a treatise on Gita, called as Gyaneshwari. In the sixth chapter, he very sweetly described the nature of this fourth power, called the Kundalini, which rests in the triangular bone and the way it is awakened by some great soul, by which one gets his fourth state of awareness.
He did not take permission from his guru to give realisation to others but he only asked that he should be permitted, at least, to write about it. Later on, this sixth chapter was not understood by the people who were in charge of religion (dharma martandas). They said that this sixth chapter was not to be read (nishiddha) and thus this great chapter was completely neglected by the people and they just tried to follow the path of bhakti, which means devotion to God, by chanting the names of God, or singing the praise of God Almighty.