A rare first edition copy of Sir Isaac Newton's Principia Mathematica has sold for a record $3.7m at Christie's, more than doubling its $1.5m estimate.
That makes it the most valuable science text ever sold at auction, smashing the previous record - which stood at $2.5m for King James I's own copy of the Principia in 2013.
The full title of the work is the Philosophiae Naturalis Principia Mathematica. Published in 1687, it lays out the foundations of modern physics and is considered an enormous leap forward in scientific thinking.
Very few first editions have ever appeared on the market.
This is the European edition of the book and differs slightly from the British version. About 80 were earmarked for distribution on the continent, out of an initial run of around 400.
Keith Moore of the Royal Society Library told the Guardian newspaper before the sale: "People who have big books these days maybe are the kinds of people who have made their money on the internet or the web...
"If you have a few million quid to spend, why wouldn't you buy a copy of Principia Mathematica?
"If you've made your money from a really cool algorithm, you will probably appreciate Newtonian physics."