Codex Madrid I

It is difficult to accurately date this copy as da Vinci's writings demonstrate a work in progress. For this reason, although the manuscript specifies two dates—September 28, 1497 and January 1, 1493—it is difficult to attribute either of the dates mentioned to its creation in its totality.

The different issues addressed in this manuscript tend to be dealt with in a single rectangular space or sheet, as seen in the image.

In certain cases, this limitation required da Vinci to move the text into the margins, or even to alter its placement based on the available space on earlier or subsequent pages.

"If the air moves, crossing the line of fire obliquely or horizontally, the effects of the projectile that follow cannot be described here due to lack of space."

The majority of the document presents very detailed diagrams of various mechanisms and gadgets, including endless screws, drive chains, textile machines, clock-making machinery, weapons, or locks …

… that in some cases take up almost the whole page; the pieces are labeled with the letters of the alphabet, and their corresponding explanations can be found in the accompanying text.

Da Vinci devoted a great deal of effort and creativity to all the elemental parts of the modern-day bicycle, almost four centuries ahead of its time! In the study on chains, which appears on page 10r, he presented a number of solutions.

The text is brimming with personal annotations that reflect the nature of this genius' mind. Below are some quotes from the manuscript:

"When a rule is confirmed by two distinct points and experiences, that rule shall be designated general."

"It is a true and known fact that nature cannot be deceived by any human ingenuity."

"How admirable it is to consider how nature operates in all its roles, and which laws have been used to establish the effects of every cause, and how it is impossible to modify them in the smallest way."

"He who denies the reason of things publicly declares his ignorance."

Codex Madrid I closely corresponds to the Codex Atlanticus, held in the Ambrosian Library (Biblioteca Ambrosiana) in Milan: a series of elements (scales, weights, gears, springs, clock-making machinery, screws, hinges, etc.) are outlined in the Codex Atlanticus, and developed in the Codex Madrid, with highly detailed and high-quality drawings. 

Links have also been identified with the Codex Forster and the Manuscript H in the Institut de France in Paris.