“That which is Below corresponds to that which is Above, and that which is Above corresponds to that which is Below, to accomplish the miracles of the One thing.”—Hermes Trismegistus, The Emerald Tablet
"As a visible phenomenon, Mercury retrograde is essentially a disappearing act. Mercury appears high in the west at dusk (evening elongation), gradually disappears below the horizon to join with the sun (inferior conjunction), and then re-appears high in the east at dawn (morning elongation). Mercury’s retrograde motion is therefore synonymous with a journey into hidden or concealed realms...significantly, all three events always happen near the same zodiacal degrees,—above, below, and above are indeed all One! Herein lies the deep profound magic of Mercury’s dance...
Nigredo, albedo and rubedo—this is the hidden order within the apparent chaos of Mercury retrogrades and in fact the pattern we can expect whenever we journey from the known into the unknown. They are like three gates or doors we pass through on any journey in search of wholeness. These three gates represent passages to three worlds, and three primary aspects of our psyche, the tria prima of self."
—Gary P Caton, Hermetica Triptycha: The Mercury Elemental Year, with Ephemerides (1925-2050)