According to my research, all the MMY mantras come from the Sri Vidya tradition which is in turn based on the "Shat Chakra Nirupana," which elaborates on the seven chakras corresponding to the seven states of consciousness in the subtle body.
You will find illustrations of the chakras along with the vertical axis of the spine and the various petals that emanate from each chakra, and the diagram of the Sri Yantra mandala.
There are numerous commentaries explaining the esotericmeaning of the Sri Yantra and the mode of worship, such as the commentary by Lakshmidhara on Sound Arya Lahari and on the Ananda Lahari, both composed by the Adi Shankara. There is a chapter in the Tripura Upanishad and one in the Bhavano Upanishad and the importance of the importance given to the worship of Sri Yantra.
Worship of the Sri Yantra is as interesting as it is complex: it is ritualistic, abstract and esoteric, and yet the Sri Yantra is one of the most meaningful and useful symbols that has been handed down to us from the Adi Shankaracharya: The essence of the vibration is the ecstatic self-recurrent consciousness.
Impelled by universal welfare, the Adi Shankara gave great importance to Sakti worship. And to this end, the Adi Shankara installed a Sri Yantra in at places of Sakti worship.
The very quintessence of the Sri Vidya is a chapter which deals with the fundamentals of the ancient mystic syllables that constitute Devi worship and the relevance of simple worship of Sri Saraswati - Lalita - Tripurasundari and the place where the Sri Yantra is installed.
There is also the life story of Bhaskararaya which shows how effective are the mystic diagram and the mantras used in the meditation on Devi Shakti.
The most complex yantra, like the Oregon yantra, is the Shri Yantra of the tantric school of Sri Vidya. Khanna says that the structure of this yantra is described in the Shankara's Saundaryalahari (Wave of Beauty). "Mantras, the Sanskrit syllables inscribed on yantras, are essentially 'thought forms' representing divinities or cosmic powers, which exert their influence by means of sound-vibrations."
Works cited:
Sri Saraswati : The Goddess of Knowledge (Sakti Darsan 6)
by T.R. Ramachandran
Tattvaloka Publication, Sri Sharada Peetham, Sringeri
p. 112
'Yantra: The Tantric Symbol of Cosmic Unity'
by Madhu Khanna
Inner Traditions, 2003
p. 21
Other titles of interest:
'Meditation Revolution: A History and Theology of the Siddha Yoga Lineage'
by Paul E. Muller-Ortega and Douglas Brooks
Agama Press, 1997
'The Doctrine of Vibration: An Analysis of the Doctrines and Practices of Kashmir Shaivism'
by Mark S.G. Dyczkowski
Albany, New York: State University of New York Press, 1987
Post by p***@gmail.com"SBS's guru was Swami Krishananda Saraswati of Sringeri, founded by the Adi Shaknkaryarya. It is incumbent on every Saraswati sannyasin to meditate at least twice a day and to perform internal puja to the Sri Yantra."
https://groups.yahoo.com/neo/groups/Shankaracharya_Swami_Brahmanand_Ji/conversations/messages/208
Post by P.N.http://youtu.be/u16wjc01ys0
Movie footage of Guru Dev, Shankaracharya Swami Brahmananda Saraswati,
believed to have been filmed in Lucknow, India, circa April 1952. Visible in
certain frames is a young man later to become world famous for introducing
millions to the practice of transcendental meditation, Maharishi Mahesh
Yogi.