Microsoft cofounder Bill Gates made headlines in 1994 when he spent an incredible .8 million on a single book. The Codex Leicester, a compilation of handwritten scientific notes by one of the greatest brains in history, Leonardo da Vinci, was not just any book, though. Gates continues to draw inspiration from its pages over twentyfive years later. But why does one of the most prosperous businessmen in the world still find this centuries-old document so fascinating, and what makes it so unique?
What is the Leicester Codex?

Leonardo da Vinci penned the 72-page Codex Leicester manuscript in the early 1500s. It is jam-packed with thorough notes and illustrations about the cosmos, nature, and science. Leonardo wrote about fossils, the moon’s shine, water movement, and even the potential for using rivers to generate energy. His writings contained concepts that scientists would not completely comprehend for generations, making them more than merely observations.
How Did the Codex Leicester End Up With Bill Gates?
Before Gates bought it, the Codex Leicester had a long journey through history. After Leonardo’s death, his manuscripts were passed down to different owners. In the early 1700s, the manuscript was acquired by Thomas Coke, the Earl of Leicester, which is how it got its name. It stayed in the Leicester family for over 250 years.
In 1980, American billionaire Armand Hammer bought it for .1 million, renaming it the “Codex Hammer.” After his death, the manuscript went up for auction again in 1994. This time, Bill Gates won the bid, paying a record-breaking .8 million—making it the most expensive book ever sold at the time.
What Made Bill Gates Purchase It
For Gates, the Codex Leicester represented human ingenuity and curiosity rather than merely being a collectible. He has always respected Leonardo da Vinci as a thinker who bridged disparate realms of knowledge as well as an artist.In addition to being an inventor, Leonardo was also a scientist, engineer, and painter. Gates’s success in business and technology has also been influenced by his interdisciplinary thinking. Gates sought to understand the mind of one of the greatest thinkers in history by examining Leonardo’s notes.
What’s Inside the Codex Leicester?

Although there are many scientific subjects covered in the Codex Leicester, water is one of its primary concerns. The way water flows across rivers, erodes soil, and can be manipulated captivated Leonardo. Many of his hydrodynamics theories were well ahead of their time and are still applicable today.
He also wrote about astronomy. One of his most remarkable observations was about the moon’s glow. Leonardo theorized that the faint light on the dark side of the moon (now called planetshine) was caused by sunlight reflecting off Earth. This idea was later proven to be true—centuries after he first wrote it down.
How the Codex Leicester Inspires Gates Today
Bill Gates has said that reading the Codex Leicester reminds him of the importance of curiosity and lifelong learning. Leonardo da Vinci questioned everything around him, constantly seeking to understand how the world worked. That same mindset has been key to Gates’s success in technology, business, and philanthropy.
Gates’s view in interdisciplinary thinking—that significant ideas occur when several domains of knowledge intersect—is also supported by the document. In addition to being a scientist, Leonardo was also an inventor, engineer, and artist. In a similar vein, integrating many fields of expertise has led to some of the most significant advancements in contemporary technology.
Sharing Leonardo’s Genius With the World

After buying the Codex Leicester, Gates wanted to make it accessible to as many people as possible. He had the pages digitally scanned and even included some of them as screensavers in Windows 95, allowing millions of people to see Leonardo’s work.
He also lends the manuscript to museums around the world, so the public can experience it firsthand. Instead of keeping it locked away in a private collection, Gates has ensured that others can learn from Leonardo’s ideas, just as he has.
The Timeless Wisdom of Leonardo da Vinci
Leonardo’s concepts are still applicable today, which is what makes the Codex Leicester so unique. Even though he lived more than 500 years ago, his methods of observation, critical thinking, and cross-disciplinary connections are still useful today. Purchasing the Codex Leicester was not solely motivated by the desire to own a rare artifact.It was about obtaining insight into the ideas of a genius, motivating the future, and learning from the past.Whether in business, science, or technology, Leonardo da Vinci’s legacy is still felt today, and people like Gates are striving to make sure it endures for many more years.