I don't want to publicize Bill Gates *S*, but he bought Leonardo's Codex Leicester, a folio of scientific observations and illustrations on natural phenomena. I could see it in a exhibition a couple of years ago. It's where he wrote (backwards!) his (in many cases, prescient) observations about the natural world. Before bringing the Codex to the United States, Gates allowed the manuscript to be shown in da Vinci’s native Italy, in France... and in Portugal, Lisbon *S*

Here you can see some of Leonardo's manuscripts: