Memory Crossing

A memory crossing is a highly complex form of mental visualization developed by Aloysius Pendergast. It combines Tibetan meditation techniques from the Chongg Ran discipline with concepts from  Giordano Bruno's Ars Memoriae (Art of Memory) and Alexander Carêem's Nine Levels of Consciousness.

The technique allows him to place himself in a state of pure concentration, where his mind could then combine all the facts and intuitions about a topic and turn it into a four-dimensional scene that could not only be analyzed but experienced. Through a memory crossing, Pendergast could reconstruct events from the past in his mind as if he were actually there, allowing him a unique forensic perspective.

History
Pendergast had long ago spent time at the remote Gsalrig Chongg monastery in Tibet, learning the esoteric mental discipline of Chongg Ran. Chongg Ran is one of the least known of the Tibetan mind techniques, invented by Confucian sage Ton Wei during the T'ang Dynasty and refined at the Tenzin Torgangka monastery in Bhutan. As Chongg Ran has no written record and is only passed directly from teacher to pupil, Tenzin Torgangka and Gsalrig Chongg are the only repositories in the world preserving its teachings. Pendergast and Constance Greene are the only two masters of the discipline outside of Tibet.

Pendergast's memory crossing technique combines Chongg Ran with the method of loci, an architectural mnemonic in which he has mentally recreated the entirety of his childhood home, the Maison de la Rochenoire, as a memory palace: a meditative storehouse to hold his memories, experiences, and observations. In this meditative state, he is able to freely roam the halls of Rochenoire entirely in his mind, searching through memory constructs for information that for whatever reason may be otherwise unable to easily recollect.

Process
Creating a memory crossing is mentally draining and requires much preparation on Pendergast's part. He begins by laying very still for several minutes, arranging facts in his mind. He then frees his mind from all distractions, particularly his own inner monologue, by utilizing various forms of mental exercises, including solving complex mathematical equations, simulating a game of bridge with four players, or playing through several rounds of speed chess.

Then begins the ancient steps of Chongg Ran itself, as his senses become acutely aware of his environment, visualizing every detail of his surroundings as if he were seeing them with his own eyes. One by one, he begins to shut off the external scents, sounds and sensations and finally the landscape itself, until he reaches stong pa nyid: the State of Pure Emptiness.

It is in this state where Pendergast merges in his mind the thousands of facts, observations, suppositions and hypotheses and slowly begins to rebuild the landscape. Now, still within his mind—as with his memory palace of Rochenoire—he is able to explore the area and experience historical events as they play out around him. This unique perspective has afforded him remarkable insights that would have been unobtainable any other way.

Deployment (Spoilers)
Pendergast has used the technique several times in the course of his investigations.
 * In The Cabinet of Curiosities, he explored the Five Points neighborhood circa 1881, including a tour of J.C. Shottum's Cabinet of Natural Productions and Curiosities


 * In Still Life with Crows, he experienced the Medicine Creek Massacre of 1865, origin of the "Curse of the Forty-Fives"
 * In The Wheel of Darkness, he used Chongg Ran as a last line of mental defense against the tulpa, ultimately fleeing to his Rochenoire memory palace, where he encountered his brother Diogenes in their old childhood hiding spot they had dubbed Plato's Cave
 * In Cold Vengeance, he visited his memory palace in contemplation of the revelation that his long-dead wife Helen was still alive, although he was again redirected to Plato's Cave for another conversation with his brother
 * In Two Graves, he confronted the memory of his now truly deceased wife about the many secrets she had kept from him


 * In White Fire, he eavesdropped on a legendary conversation between the authors Arthur Conan Doyle and Oscar Wilde at a ski lodge in Colorado
 * In Blue Labyrinth, he witnessed the night his son Alban saw his wife and unborn child burned alive in their home, and then looked on as Alban single-handedly staged a bloody coup
 * in Crimson Shore, he watched the 1884 shipwreck of the SS Pembroke Castle and the mass murder of the surviving women and children
 * In Verses for the Dead, he undertook a memory crossing at the site of Elise Baxter's suicide eleven years earlier