The manuscripts Leonardo left us are the main source for those who want to study the life and works of Leonardo: in them are the preparatory studies for many of his paintings, as well as his studies on engineering, anatomy, architecture, mechanics, ballistics, and the flight of birds. Initially conceived as pages of notes to improve the quality of his paintings (anatomy studies for the portrayal of the human body, botanical studies for plants, and geology for rocks), in time Leonardo’s notebooks became something more: a register of his interests and of his progress in each field.

Written mostly in “mirror writing,” i.e. from right to left, the codices never cease to intrigue scholars: some historians maintain that they were written to kindle the unknowing reader’s curiosity, others that it was simply faster for Leonardo to write in this fashion because he was left-handed. Reading these texts, you perceive an intellect that doesn’t limit itself to the authority of past authors but rather challenges concepts with the experience of Nature. The laws of Nature are expressed in mathematics: “No human invention can sustain the fact that it is truly science if it does not pass through mathematical demonstrations,” with the general understanding that “should you say that sciences, which originate and end in the mind, are true, it is in fact a false statement, for many reasons; first and foremost, that in these mental discussions no real experience occurs, without which nothing is certain.” It is a marked refusal of metaphysics, coherent with Renaissance anthropocentrism.

Leonardo’s manuscripts, inherited by Francesco Melzi, after the latter’s death, were passed onto sculptor Pompeo Leoni, who, with the intent of selling them, divided them into separate lots, thus changing their original disposition. Collected for the most part in the 17th century by the Milanese Count Galeazzo Arconati, they were donated to the Biblioteca Ambrosiana in Milan, from where they were transferred to Paris in 1796. After Napoleon’s fall, only the Codex Atlanticus was returned to Milan, while the others, because of an error by Austrian officials, remained at the Institut de France. Other codices had ended up in England many years earlier.

Today there are over 8,000 sheets of notes (over 16,000 pages) with many dozens of thousands of drawings by Leonardo, but these are considered to be only a small part of what the master from Vinci had actually put down on paper. Some think that he produced around 60,000, or even 100,000 sheets, mostly all of which are now lost. Possibly, though, there are still manuscripts to be discovered buried in ancient archives. In 1966, for example, two new codices were found in Madrid. These pages appear to have been written “all in one go,” so much so that Leonardo experts say: “it is like hearing him in a recording”.