The Tibetan meditation practice that used the Antahkarana took place in a room lit with candles. In the middle of the room was a large earthenware vessel shaped in an oval which symbolized the cosmic egg of the universe. The vessel was filled with several inches of water and in the middle was a stool. On the seat of the stool, inlaid in silver was the Antahkarana Symbol. One wall was covered with copper that was polished to a mirror finish. Tapestries which displayed Reiki symbols were hung on the opposite wall. A Tibetan Lama meditator would sit on the stool and gaze steadily at the image of the Reiki symbol reflected in the polished copper mirror. This yantra meditation would create one-pointedness in the mind of the meditator, uniting the consciousness with the transcendental energies of the Reiki Symbol while the Antahkarana Symbol on the stool would focus the energies generated and cause them to evenly flow through all the chakras and to connect with Earth.
It is clear that the Tibetans did not originate the symbol and there is no written record as to its true origin. However, through clairvoyent perception the symbol was first given to the people of Earth during Lemurian times over 100,000 years ago. This was the same time Reiki was first brought to Earth by the Holy Spirit. The Antahkarana was created by a counsel of Ascended Masters who are watching over the evolution of the Galaxy. They saw that the people of Earth were in trouble and needed help in re-establishing their connection with the Higher Self. They created the symbol and using a decree, imbued it with its own consciousness. Now anyone who uses it will have the connection between the physical brain and the Higher Self strengthened. It is the Higher Self that creates and guides the benefits of the symbol and that is why it can never be used for harm.
Source: International Center For Reiki Training