Jakob Bohme (also spelled Jacob Boehme), was a German mystic and theologian who lived during the 16th and 17th centuries. De Signatura Rerum (The Signature of All Things), was written in 1621 and is considered his greatest work. From the preface: "THIS book is a true mystical mirror of the highest wisdom. The best treasure that a man can attain unto in this world is true knowledge; even the knowledge of himself: For man is the great mystery of God, the microcosm, or the complete abridgment of the whole universe: He is the mirandum Dei opus, God's masterpiece, a living emblem and hieroglyphic of eternity and time; and therefore to know whence he is, and what his temporal and eternal being and well-being are, must needs be that ONE necessary thing, to which all our chief study should aim, and in comparison of which all the wealth of this world is but dross, and a loss to us."