Written in Leonardo's famous mirror-script between 1506 and 1510, the Codex Leicester contains his observations on astronomy, fossils, and the movement of water.
It offers a direct, handwritten window into how one of history's greatest minds actually thought.
Bill Gates bought it at Christie's in 1994 for $30.8 million, a record that has stood for three decades.
Pages from the manuscript have reportedly been digitally scanned and occasionally displayed as screensavers — because owning a Da Vinci apparently isn't enough; you should get to look at it whenever you want.
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