In the winter of 1909 Aleister Crowley and Victor Neuburg walked through the Algerian desert calling the thirty Enochian Aethyrs, the successive worlds named in the material John Dee and Edward Kelley had received three centuries earlier. Crowley scried and spoke; Neuburg wrote, and took a working part in the ritual as well. The record was published as The Vision and the Voice, and it is the fullest first person account of sustained Enochian practice in the modern literature.
The episode that everything else in it turns on is the tenth Aethyr, worked on a mountain near Bou Saada, in which the entity named Choronzon is called into a circle of sand and Neuburg, inside the circle with a knife and a book, has to record what happens while it attempts to break out. The event is presented in the tradition as the crossing of the Abyss, the passage in which the practitioner surrenders individual identity. The atlas records it with the qualification that has to accompany any such account: the record is the only source, both participants had a stake in what it described, and nothing about it is independently witnessed.
The Aethyrs themselves are worth explaining, because the working is unintelligible without them. The Enochian material received by Dee and Kelley includes thirty named regions, each entered by reciting a call in the Enochian language with the name of the Aethyr inserted, and each governed by named spirits. Crowley worked them in reverse order, from the outermost inward, which is how the tenth comes so late in a sequence of thirty and why the record builds toward it rather than reaching it in passing.