The Codex Leicester is a 36 pages notebook compiled in 1508-1510 by Leonardo da Vinci (1452-1519) comprising notes, comments and sketches on water, cosmology and even submarine warfare whose particularity is to be written from right to left using his characteristic mirror writing.
It was originally bought by Thomas Coke, 1st Earl of Leicester in 1717. In 1980 it was offered for sale to pay for tax liabilities of the 5th Earl of Leicester. At that time art authorities in Milan asked 29 private banks in Italy to bid for it but to no avail. The Codex went on auction to Dr. Armand Hammer for $2.2 million who stupidly enough renamed it the Codex Hammer. Hopefully a billionaire a little less pretentious named Bill Gates bought it in 1994 at auction for $ 30.8 million, making it the most expensive book ever, and renamed it the Codex Leicester. The Codex is put on public display once a year in a different city around the world. It is currently under the 14th of September 2008 exhibited in the Houston Museum of Natural Sciences where a more general Da Vinci exhibition is held.
Currently, the Codex Leicester notebook authored by Leonardo da Vinci is in the possession of Microsoft Chairman Bill Gates. However, there is nothing stopping you from shuffling through its pages. You will be able to browse through Codex Leicester or Codex Arundel, both notebooks of da Vinci and even have a look at one of the oldest copies of the New Testaments Codex Sinaiticus.
This is possible via the Turning the Pages 2.0, an online program over at the British Library. Turning the Pages is a browser based Windows Presentation Foundation application that allows users to turn the pages of old books in a virtual environment.