The notebook, one of about 30 books produced by da Vinci during his lifetime on a wide variety of subjects was written around 1508. It contained 72 loose pages and featured 300 notes and detailed drawings. All the notes and drawings related to the theme of water and how it moved.

The text was written in brown ink and chalk and read from right to left. It was an example of his favored mirror writing technique. The notebook was discovered in 1690 by the painter Giuseppe Ghezzi in a chest  of papers belonging to a 16th century Milanese sculptor who had previously studied and admired da Vinci’s work. In 1717 the manuscript was bought by Thomas Coke, the first Earl of Leicester, he added it to his impressive collection of art at his families estate in central England.

It remained with that family for over two centuries, and became known as the Leicester Codex. In 1980 the current Lord Coke was forced to sell to cover inheritance taxes on the estate and its art collection. In the days preceding the sale art experts predicted it would sell for something in the region of $7 to $20 million. When the sale of this lot began, bidding started at $1.4 million and lasted less than two minutes.

Armand Hammer and two or three rival bidders were competing and the price raised by $100,000 with each bid. The winning bid of $5.12million was the highest price paid for a manuscript at that time. Hammer was later reported to have said ‘I am very happy with the price, I expected to have to pay more. There was no work of art in the world I wanted more than this.’ The seller on the other hand was not so happy, Lord Coke was said to be only reasonably happy and claimed the proceeds would not be sufficient to cover the taxes he owed.

Hammer was the president of the Occidental Petroleum Corporation, he renamed his prize the Hammer Codex and it was added to his collection of art. Hammer died in 1990 and he left this and other works of art to the Armand Hammer Museum of Art and Cultural Centre at the UCLA. Some years later the manuscript was again on sale after the museum said it was forced to take this action to cover legal costs when the niece and sole heir of Hammer’s late wife sued claiming Hammer and his late wife had cheated her out of her rightful share of his fortune.

On the 11th of November 1994, the Hammer Codex was sold to an anonymous bidder. The bidder was later identified as Bill Gates, the founder of the Microsoft empire. At the New York auction the manuscript was sold for a new record high of $30.8 million. Bill Gates restored the title of Leicester Codex and he has since loaned the notebook to a number of museums for public display.