Thomas Merton notes in his journal that he has much to read. "Tucci's "The Theory and Practice of the Mandala", Desjardins' "Message des Tibetains", the Dalai Lama's pamphlet on Buddhism, essays by Marco Pallis, Trungpa..."
The Mystical Mandala
Merton seems most fascinated with the Mandala and makes extensive notes from Giuseppe Tucci's book. I've looked at a number of definitions and descriptions of the Mandala and find that Wikipedia is a pretty good start
Mandala (Sanskrit "circle", "completion") is a term used to refer to various objects. It is of Hindu origin, but is also used in other Dharmic religions, such as Buddhism. In the Tibetan branch of Vajrayana Buddhism, they have been developed into sandpainting. In practice, mandala has become a generic term for any plan, chart or geometric pattern that represents the cosmos metaphysically or symbolically, a microcosm of the Universe from the human perspective...
...In various spiritual traditions, mandala may be employed for focusing attention of aspirants and adepts, a spiritual teaching tool, for establishing a sacred space and as an aid to meditation and trance induction. Its symbolic nature can help one "to access progressively deeper levels of the unconscious, ultimately assisting the meditator to experience a mystical sense of oneness with the ultimate unity from which the cosmos in all its manifold forms arises." The psychoanalyst Carl Jung saw the mandala as "a representation of the unconscious self," and believed his paintings of mandalas enabled him to identify emotional disorders and work towards wholeness in personality." Wikipedia
Thomas Merton quotes Tucci in describing the Mandala as a map of both the cosmos and the soul... "the disintegration of the One to the many and the reintegration from the many to the One..." AJTM p.59
Be whole... Rob
"From the body of the unborn essence arises the sphere of light, and from that sphere of light arises wisdom. From the wisdom arises the seed syllable and from the seed syllable arises the complete Mandala, the deity and the retinue." Tenzin Wangyal Rinpoche