The roots of technical writing are deeply planted in the field of mining engineering, with its emphasis on economics, value, and social stability. In the mid-16th century, Georgius Agricola published "De Re Metallica," a compilation of knowledge about mining and metallurgy. Agricola sought to explain the reasoning behind some of the recipes for manipulating nature that he had taken from textual sources. In the 16th century, magic included all practices based on experiential knowledge which sought to manipulate nature. According to this formulation, Hermetic knowledge contained in books of secrets certainly was magical and knowledge about the physical world gained from practical experience, like that of mining and metallurgy, could also be considered magical. Agricola's introduction to "De Re Metallica" also worked to differentiate his text from books of secrets. Instead of recounting how the information contained in the book was revealed to him in a personal encounter with a god--a generic literary device for giving books of secrets their authority--Agricola built the authority for his text on his own experience and that of people to whom he had talked and whose texts he had read. Agricola was one in a string of writers who compiled useful information into handbooks after the development of the printing press made these compilations profitable for press owners, publishers, and writers. Many people benefitted from such knowledge. (Contains 6 references.) (CR)