Sir Isaac Newton is largely renowned for watching an apple fall to the ground -- in 1666.

While the event has become iconic as a "eureka" moment of inspiration, most creativity experts grasp that Newton's genius stemmed from the decades of hard work following that moment. "What most people forget," James Clear notes in Quartz, "is that Newton worked on his ideas about gravity for nearly twenty years until, in 1687, he published his groundbreaking book, The Principia: Mathematical Principles of Natural Philosophy. The falling apple was merely the beginning of a train of thought that continued for decades."

Which means that the juiciest insights into how Newton worked can come from examining his habits before and after the apple. Thanks to a recent post by the Royal Society of London, you now have a chance to learn about one of his most important habits: the way he read books. Specifically, his tendency to "dog-ear" pages that were important to him. 

In fact, the Royal Society -- with tongue firmly in cheek -- gives Newton a good old-fashioned librarian's reprimand. Rupert Baker, the Royal Society's library manager, calls Newton "a serial offender in the area of page-corner tampering." All told, the Royal Society has four books from Newton's personal library in its collection.

  • Samuel Foster's Miscellanies: or, Mathematical Lucubrations (1659) 
  • A treatise on numismatics from 1700
  • A 1610 Basle edition of the Artis Auriferae, a collection of tracts dealing with alchemy
  • Heinrich Cornelius Agrippa's De Occulta Philosophia (1533), which was about occult philosophy and ritual magic.

Only the first title directly relates to Newton's study of gravity, which is why this quartet of books is fascinating in its own right. It shows Newton's interests were wide-ranging. Like Van Gogh and Einstein, Newton was a Janusian thinker, someone who could mix and combine seemingly disparate fields to stimulate creative breakthroughs.

Beyond this, there's the way Newton dog-eared these books. To learn more about Newton's dog-earing methods, Baker consulted a book called The Library of Isaac Newton by John Harrison (1978). Here are Baker and Harrison's insights: 

Newton dog-eared pages in a very specific way. 

The common way to dog-ear a page is to fold a corner of the page down or up (depending on whether you're folding the upper or lower corner of that page). Newton took it one step further. He made sure the tip of the dog-ear pointed exactly to the pertinent part of the text. "A sentence, phrase, or even a single word," writes Baker. 

Newton took extensive notes in the book itself. 

His marginalia is extensive. There's so much of it, "marginalia" almost ceases to be an accurate word for it. His notes are copious, often occupying the entirety of a page's white space. 

Newton was exceptionally organized as a note taker. 

In addition to taking up most of the margins with notes, Newton created handwritten indexes and contents lists. The indexes look like present-day indexes: They are alphabetical, by topic. They list page numbers directly after each topical listing. You can surmise how marvelously these indexes complemented his dog-earing habit. 

Newton wasn't afraid to damage the books.

It's a basic point, but it shouldn't be overlooked. Books are property. Sometimes they are valuable property. Newton's physical use of them "clearly reflects Newton's attitude that books are working tools to be used as convenient and to destruction," notes Baker.

Mind you, Baker doesn't want any visitors to the Royal Society library getting the wrong idea. Dog-earing, he notes, is a "habit of historical interest when found in the former possessions of a genius, but present-day culprits will not be treated quite so understandingly," he writes. "The Librarian Death Stare is an actual thing, you know."