Isaac Newton's handwritten notes for a second edition of his masterwork, the "Principia," are set to go under the hammer next month, auction house Christie's said on Tuesday.

The London-based auctioneer expects the pages to reach between 600,000 and 900,000 pounds ($850,000 to $1.3 million; roughly €700,000 to €1.1 million) when they are sold on July 8.

Revising the 'Principia'

First published in 1687, Newton's "Philosophiae naturalis principia mathematica," or "Mathematical Principles of Natural Philosophy," set out the laws of gravitation and motion.

The book "reinvented our understanding of the universe," Thomas Venning, head of books and manuscripts at Christie's in London, told the Associated Press.

During the 1690s, Newton began working on a planned second edition of the work, producing the page and a half of notes set to be auctioned. They also include comments and diagrams by Scottish mathematician and astronomer David Gregory.

The two scientists met and corresponded while Newton was working on his revisions.

Keith Moore, head librarian at the Royal Society, the scientists' club where Newton was president in the 18th century, said the partnership between Gregory and Newton has "resulted in refining Newton's thinking."

Newton eventually gave up on the revisions in question, before ultimately producing a new edition in 1713.

How important are the notes?

The notes are particularly rare due to Gregory's contribution, Venning said.

Venning described the document as showcasing "the greatest minds in history, talking about their greatest achievements."

A first edition of the Principia sold at auction for $3.7 million in 2016, becoming the most expensive science book ever sold.

kmm/msh (AP)