Bill Gates Paid $30.8 Million for Leonardo da Vinci's Notebook — What Did He Buy?

The Notebook That Sold for $30.8 Million

On November 11, 1994, Christie's auction house in New York sold a slim notebook of 72 pages to a technology billionaire for $30,802,500. The notebook was approximately 500 years old. It had been written in mirror script — right to left, in Italian — by Leonardo da Vinci, and it contained his scientific observations and speculations about water, rock strata, fossils, the nature of light, and the movements of celestial bodies. Bill Gates, who had built one of the world's most valuable companies on the power of information, apparently found it worth the price.

The Codex Leicester — named for Thomas Coke, the Earl of Leicester, who purchased it in 1717 — holds the record as the most expensive book or manuscript ever sold at auction. Gates's purchase price in 1994, adjusted for inflation, represents an extraordinary sum for handwritten pages that most people will never read in their original form. What Gates saw in it, and what he did with it afterward, says something interesting about why the notebook is worth studying even five centuries after it was written.

What Leonardo Wrote

The Codex Leicester was composed between approximately 1506 and 1510, when Leonardo was in his mid-fifties and living in Florence and Milan. It is not a unified text with a single argument — it is a working notebook, filled with observations, questions, diagrams, and hypotheses that Leonardo pursued with restless intellectual energy.

Much of the notebook concerns water in all its manifestations: how rivers erode their banks, why the sea does not overflow despite receiving water from rivers, how waves and currents behave, why fossils of marine creatures appear in mountains far from the ocean. On this last point, Leonardo reached a conclusion that was radical for his time: these fossils were the remains of actual organisms that had once lived in ancient seas. The mountains, he argued, must have once been beneath the ocean. This was a proto-geological insight that mainstream European thought would not fully accept for another two centuries.

Leonardo also wrote extensively about the nature of light and its behavior in the atmosphere, attempting to explain why the sky is blue and why the Moon appears to glow even in shadow (because of earthshine — reflected light from Earth). His answers were not always correct by modern standards, but his method — systematic observation, logical reasoning, willingness to question received authority — was centuries ahead of its time.

Gates, Digital Access, and a Five-Century Document

After purchasing the Codex, Gates did something that Leonardo himself might have appreciated: he had it digitized and made available to the public. The Codex Leicester was one of the first major manuscripts to be digitally reproduced and distributed, with a CD-ROM version released in 1994 that allowed ordinary readers to zoom into individual pages, read translations, and follow Leonardo's arguments across the notebook.

The physical manuscript has since been exhibited at major museums around the world, including the Seattle Art Museum and institutions in Italy and Japan. Each exhibition loans the pages in small batches — the notebook is disbound for display — allowing visitors to see Leonardo's handwriting, diagrams, and marginalia directly.

The question of what makes a 500-year-old notebook worth $30 million has a simple answer: it is one of the only surviving windows into the mind of someone who may have been the most comprehensively curious person who ever lived. That seems like a reasonable price.