Sir Isaac Newton ( 4 January 1643 -31 March 1727). English physicist and mathematician. 18th Century Mezzotint portrait after the painting by Sir Godfrey Kneller 1689, with later colouring. It shows Newton in his prime and is the earliest of the portraits. Newton is famous for his laws of motion and gravitation and remains one of the greatest scientists of all time. His opus magnus was his \Philosophiae Naturalis Principia Mathematica\". Other pursuits included optical physics, alchemy, religious and occult investigation, and preventing forgery while superintendant of the Royal Mint. He was widely viewed as an eccentric genius, but his human remains indicated mercury poisoning from his alchemy may have contributed to his instability. This version retains yellow age toning of original and is in the possession of the photographer."