Bellicorum instrumentorum liber,  Book of warfare devices, is a fascinating and absorbing inventor’s notebook. The title was bestowed by someone else, and it’s misleading as to the contents, which cover a very wide range of ideas.

Sometimes we try to invent something new by exploring within the bounds of what is known to be possible, and sometimes we invent by expanding those limits. For an imaginative engineer in the early fifteenth century — working more than two hundred years before the discoveries of Newton — the process of invention would be often a curious mix of the two. You would know so little about mechanical force that you could conjure up almost anything and believe it to be practical. Of course, attempts to bring the designs to reality would often fail, but they might, on occasion, also succeed.

Suppose for a moment that you were such a person possessing a talent for gadgets in the early fifteenth century, or an engineer hoping to build marvelous machines and clever structures no one else had yet dreamed of — how would you go about showing your talents? And what if you were someone who wanted to own wonderful and mysterious devices, such as a prince — how would you find the person who could make these things? A remarkable testimony to this meeting of engineering skill, technological ignorance, individual initiative, and public demand can be found in the Bavarian State Library, in the sketchbook of an Italian inventor of the early fifteenth century. It is a volume of sixty-eight drawings advertising the inventions that Johannes (or Giovanni) de Fontana (ca. 1395–1455), who was both the engineer and the artist, hoped to sell to patrons. Thought to have been created sometime between 1415 and 1420, the work has no title by Fontana that has survived, but a later owner gave it the title Bellicorum instrumentorum liber — the Book of Warfare Devices — despite the fact that most of it does not concern military matters.

This is an absorbing insight into thought, knowledge, and the desire to create, and you can see the whole thing here, or see selected bits along with text at The Public Domain.