John Nash was a brilliant mathematician who, over his career, made major contributions to his field. He also struggled with mental illness and his story was told in A Beautiful Mind, a biographical film starring Russell Crowe as Nash. He and his wife were killed in a car accident in May.
Nash's adviser and former Carnegie professor Richard Duffin wrote this letter of recommendation for Nash's entrance to Princeton. It says all that needed to be said: "He is a mathematical genius."
Via Cliff Pickover