Saxl pressed Warburg to travel south and visit the newly discovered mithraeum in Capua, near Naples.  He wanted an eyewitness, for in 1929 he had himself returned to the study of Mithraic monuments, reviving an old interest.  Saxl’s research would culminate in 1931 with the publication of Mithras: typengeschichtliche Untersuchungen (Mithras: investigations into the history of types). In 1929, happy to find in Warburg an interested interlocutor, he set down his emerging thoughts in lengthy letters. Various of Saxl’s ideas on Mithraic imagery surface in the aggregates of photographs that make up Panel 8.

On May 5 Warburg, Bing, and Alber left Rome for Naples, and on May 17 the excursion to Capua took place. In notes of the time on Giordano Bruno (WIA III.121)—making allusion to Bruno’s  Spaccio de la bestia trionfante (Expulsion of the Triumphant Beast)—Warburg recorded: “An einem Tage: Spaccio delle tenebre durch das äussere (Mithras) zu innerem (Giordano Br.) Licht”—“On one day: the expulsion of darkness through the outer (Mithras) to the inner (Giordano Bruno) light.” The great day had begun with a visit to the Dominican convent of San Domenico Maggiore in Naples, where Bruno had professed and where, in the Carafa Chapel, Bing, to their joy, found soffit reliefs carved with the signs of the zodiac and the fixed stars—images that might have impressed themselves on Bruno’s memory. They then traveled by hired car to Capua in a terrific storm. After comical misadventures, but still primed for wonder, Warburg climbed down a rickety ladder into the pitch dark to explore the Mithraic cave and to try to make sense of the extraordinary image cycle. On May 23 he wrote to a colleague in Rome, Eugénie Strong, describing the two experiences as crucial. The first gave access to the psychology of Bruno’s imagistic thinking, while, through the latter, he gained “thrilling and at the same time enlightening insights into the nature of the antique mysteries.”