Of Natural and Supernatural Things is a classic spiritual studies text by Bacillus Valentinus. Because I have at this present undertaken to write of the of the first Tincture, the Root of Metals and Minerals, and to inform you of the Spiritual Essence, how the Metals and Minerals are at first spiritually conceived and born corporally; it will be necessary first of all to utter, and to acquaint you by a speech, that all things consist of two parts, that is, Natural and Supernatural; what is visible, tangible, and hath form or shape, that is natural; but what is intactible, without form.
I learned quite a lot from the perspective of how 15th century Alchemists thought. Although I haven't finished the book in one long stretch. I often at times find myself going back to it and reading it. For anyone interested it can be found at http://www.gutenberg.org/files/26340/...