Move over, Dan Brown—here's a real one from the history books. The Wall Street Journal reports that a Princeton cryptologist has finally cracked a code from Thomas Jefferson's correspondence that went unsolved for more than 200 years. Jefferson's math prof buddy, Robert Patterson, created what he believed to be the perfect code and sent a block of coded text to Jefferson, a fellow cipher enthusiast, for his approval. The puzzle stood until 36-year-old mathematician Lawren Smithline solved it in 2007 by transcribing the letters into a grid, and by analyzing likely letter and number pairs using a computer. He recently described his puzzle-solving method in American Scientist.