In the supplementary volume to the two volumes of 'Mysterium Coniunctionis', Jung's student Marie-Louise von Franz edits and comments on a rare alchemical text from the Middle Ages, which provides a vivid insight into the processes described by C.G. Jung and simultaneously demonstrates how the alchemical tradition of symbols serves to express more unconsciously perceived than consciously thought psychological contents. Alchemy offered a person, who was unfamiliar with the concept of the unconscious but experienced its reality, a way to engage with this mysterious inner power. The text is significant more philosophically than historically in terms of chemistry and illustrates how the images of Christian mysticism and those of alchemy mutually permeate each other. The analysis of the text from its content revealed that it reflects an experience of the unconscious that led to a delirious state in the author, comparable to states observed empirically in people who are near death. Since history records that Thomas Aquinas died in a trance state and interpreted the Song of Songs shortly before, and since the Aurora ends with a paraphrase of the Song of Songs, the handwritten attribution of the text to St. Thomas had to be examined more closely. The not uninteresting results were presented at the end of the book. Aside from this, the commentary on the text shows how C.G. Jung's psychology can serve as a key to deciphering a chaotic and incomprehensible text in its meaning. Perhaps the most significant aspect of this text is the gradual emergence of a God-human anthropos figure, which symbolizes the wholeness of the soul and the goal of the individuation process.