A Mystic Rectangle in a horoscope involves two sets of oppositions whose ends both trine and sextile each other, thus visually forming a large rectangular pattern across the chart. Dane Rudyhar referred to it as "practical mysticism" since it involves "two potentially awareness-revealing, illuminating oppositions that can creatively reach ideal or inspired fruition (trine influence) thru intelligent, innovative utilization of energies (sextile influence). However, much depends upon the level at which the oppositions are experienced by the individual (since the opposition aspect can also express itself as disharmony, imbalance, separative forces, and irreconcilable tension). Normally, the challenges of the two oppositions are more effectively encountered than would be otherwise expected, due to the integrative influences of the linking trines and sextiles. Conflict and discord determined here now have a stimulating, encouraging impetus for satisfying resolution, suggesting that such oppositions are less prone towards being paralyzed by impasses and stalemates. Any perspective gained can here be more self-expressively utilized in a growth-producing manner. Attempts toward productive activity in relationships are better able to be more objectively evaluated and balanced in their execution thru INSIGHT and INTUITION when this configuration is positively expressed" (from page 94 of "Dynamics of Aspect Analysis" by Bil Tierney, 1983).
Thomas Merton's chart (see link below) displays a Southern Hemisphere emphasis, suggesting being swept away by events, even victimized by them in many cases. Parental tensions are highly significant, the need for love and the anxiety about being unlovable is marked, and anxiety over self-worth and self-value is salient. Relational and sexual issues also predominate, and higher education most likely interrupted. Intelligence and adaptability are located center stage, along with a sense of emotional drama. A desire to be respected, loved and honored for innovation, intellectualization, and social significance is shown to others idealistically and impressionably.
Merton's Mystic Rectangle is formed by the conjunction of Saturn (11) and AP Pluto  at the nadir, opposite his Venus (2,7) at the Midheaven, along with the opposition of his Leo 6th House South Node to the conjunction of the North Node, Mercury (4,7), and Jupiter (9,10). The South Node trines Venus, while Saturn-Pluto trines Node-Mercury-Jupiter. The South Node sextiles Saturn-Pluto, while Venus sextiles Node-Mercury-Jupiter.
In 1948, with SA Ascendant = Neptune, SA Midheaven = Mars, SA Mercury = Pluto, SA Venus = Neptune, SA Saturn = Mars, SA Uranus = Chiron, and SA Node = Pluto, Merton's famous book entitled "The Seven Story Mountain" was published! Also please note that in October of 1948 when the book was first displayed, Merton had transiting Uranus partile conjunct natal AP Pluto, transiting Venus-Saturn was conjunct natal South Node, transiting Mars-Chiron was square natal South Node and natal North Node-Mercury-Jupiter, and transiting Jupiter was partile conjunct natal Venus!!!
If he had had an astrological consultation in 1947, he would have disclosed that he had finished writing the book the previous year, but would naturally also be curious and anxious about whether or not it would eventually be published, since it appears it was undergoing some kind of litigation process in 1946 and/or 1947. Imagine being that astrologer, and then noting the aforementioned aspects soon to come to the forefront in 1948!!!
Eleven years later, in 1959, at the age of 44, on the heels of his transiting Saturn and Uranus oppositions, and upon the dawning of his year of solar arc semi-squares, he began a dialogue with noted Buddhist scholar D.T. Suzuki, on the similarities of Christian mysticism and Zen, which was later published as "Wisdom in Emptiness" in his book entitled "Zen and the Birds of Appetite." At that time, transiting Uranus and transiting Pluto conjuncted natal South Node (Node = Uranus/Pluto...Untiring colleague; teamwork paying off...Tyl), transiting AP Saturn conjuncted natal Venus and the Midheaven, and transiting Chiron conjuncted natal Node-Mercury-Jupiter!
And, not surprisingly, on the afternoon that he discarded his body in December 1968, with the backdrop of SA Mars = Ascendant and SA Chiron = Sun, all four corners of his Mystic Rectangle were also strongly activated, with transiting Pluto squaring natal Saturn-Pluto and natal Venus, and transiting Neptune squaring natal South Node and natal North Node-Mercury-Jupiter...
"Practical mysticism" in deed...thanks to the productive and fruitful activity of Insight and Intuition...http://www.astro.com/astro-databank/Merton%2C_Thomas