Isaac Newton, one of the world’s greatest mathematicians, left behind thousands of pages when he died. Numerous dead-tree collections have been published of his papers but the Cambridge Digital Library states: ” The Library holds the most important and substantial collection of Newton’s scientific and mathematical manuscripts and over the next few months we intend to make most of our Newton papers available on this site.” Those works that are now available have been transcribed for easier reading. Another ongoing electronic project can be found at The Newton Project where almost 5 million transcribed words of Newton’s writings are available online. This site also includes a listing of the books in Newton’s library that were used in his own research/writings; these are not digitized, but a quick look through some repositories such as HathiTrust or Internet Archive will pull some of them up.
Isaac Newton’s Papers Online