Which Leonardo da Vinci manuscript did Bill Gates buy at auction in 1994?

Bill Gates bought Leonardo da Vinci’s Codex Leicester at auction in 1994.

The manuscript is a collection of scientific writings and drawings by Leonardo, covering subjects such as water movement, geology, astronomy, and the nature of light. Leonardo wrote the pages in his characteristic mirror writing, intended to be read with the help of a mirror.

Gates purchased the codex from the estate of oil heir Armand Hammer. After the purchase, the manuscript was renamed the Codex Gates for a period, but it is now generally known again as the Codex Leicester.

The codex is not a conventional bound book written as a single narrative. It consists of loose sheets assembled into a substantial record of Leonardo’s observations and theories.