First published together in Latin in 1623, these two tracts, Enchyridion Physicae Restitutae and Arcanum were at once recognized to be among the clearest descriptions ever written of the hermetic cosmology and the alchemical work. They were translated into English by two leading occultists, John Everard and Elias Ashmole, and the translations are printed together here for the first time. The introduction provides the fullest biographical notice ever written about d'Espagnet, a retired public official who published the works under strict anonymity. It also traces the influence these works had on later generations of practical alchemists like Eirenaeus Philalethes and spiritual alchemists like Thomas Vaughan. The commentary traces the d'Espagnet's extensive references to classical philosophy and poetry as well as to earlier works in alchemy. The introduction discusses the life, publications, and critical reception of d'Espagnet, and suggests why the book became required reading for members of an English hermetic society. Following the text itself, a set of annotations indicates variants in the Latin original and a French translation that Everard may have seen, notes obvious mistakes in the text, suggests alternate readings, expands d'Espagnet's marginal notes into meaningful citations, and identifies further sources when possible. This edition will be of interest to scholars of alchemy, early modern science, French literature, and English literature. An index of names follows the annotations.