The third volume in the Mysterium Hermeticum series, Arca Arcanorum bears the tantalising subtitle “the Secret of Secrets.” This is Aula Lucis’ most unique and momentous hermetic publication to date. For nearly four hundred years, Arca Arcanorum existed solely as a singular manuscript written in Arthur Dee’s own hand, testifying to his self-professed achievement of the Great Arcanum. To save it from prying eyes, it was bequeathed to the Bodleian Library in Oxford, and subsequently entered the manuscript collection of the British Library as Sloane MS 1876. We are delighted to bring this all-important alchemical work into print for the very first time, with the assistance of Megan Piorko, a renowned scholar of 17th century textual culture and alchemical knowledge.

Arthur Dee was born in 1579 as the eldest son of the famed Elizabethan magus, astrologer and polymath, John Dee, with whom he shared the same birthday. From a very young age he became his father’s alchemical progeny, and accompanied him on their famous six-year expedition across Europe, which included a sojourn at the alchemical court of Emperor Rudolf II of Prague. He frequently witnessed alchemical operations performed by John Dee and his collaborator, Edward Kelley, including metallic projection and transmutation, which Arthur attests to have witnessed for the first time at the tender age of 8. Later, Arthur Dee will go on to acquire a medical degree at the University of Basel and continue his studies in Oxford, subsequently establishing a successful carrier as a physician in England. In 1621 he was recommended by King James to Tsar Mikhail of Russia, and became the latter’s personal physician in Moscow for fourteen years. It was there that he composed his only two original texts: Fasciculus Chemicus and Arca Arcanorum. The former appeared in print in Latin in 1631, and was eventually translated into English in 1650 by the admiring Elias Ashmole, who considered Arthur Dee to be one of the greatest authorities in alchemical learning among Englishmen. It was this very same edition of Fasciculus Chemicus that also featured Ashmole’s first English translation of the Hermetic Arcanum of Jean d‘Espagnet, which appeared as Vol. 1 in the Mysterium Hermeticum series in December 2023. The two tracts were, in the words of Ashmole, “suited so punctually,” that he considered them to be excellent companions.

Fasciculus Chemicus is essentially an expertly curated collection of alchemical tracts, with ten chapters corresponding to the successive order of operations in the creation of the Philosopher’s Stone. Each chapter ends in a “corollarium” written by Dee, and the entire text ends with further 21 “observanda” which provide a crucial key to the Work. Arca Arcanorum, compiled by Dee three years after the publication of Fasciculus Chemicus, is based on the latter, but brings to bear upon it the newfound light of Dee’s triumphal attainment of the Philosopher’s Stone. He includes four new canonical names, new additional material from pre-existing authors, and ten new “observanda”, among other changes, all of which must have been instrumental to Dee’s success in the consummation of the Great Work. In the Preface to Arca Arcanorum, he writes: “I have at last (by divine help) solved the riddles of knowledge. An example of this, in this climax of my life, with some select manuscripts I dedicate (under your auspices) to devotees of alchemy.”

As a further key to the alchemical processes outlined by Dee, the Appendix features the decrypted text of the alchemical cipher known as Hermeticae Philosophiae Medulla, found originally in a shared notebook which belonged to John and Arthur Dee. The cipher was finally decoded by Megan Piorko, Sarah Lang and Richard Bean in 2023. The full text of it, augmented with further details from the Scottish alchemist Patrick Ruthven’s 1612 laboratory notes, is included in this edition of Arca Arcanorum.