David Mercer:

Two math-notebook pages recently authenticated as belonging to Abraham Lincoln suggest the 16th president, who was known to downplay his formal education, may have spent more time in school than usually thought.
And the Illinois State University math professors behind the discovery say the work shows Lincoln was no slouch, either.
Math professors Nerida Ellerton and Ken Clements said Friday at the university in Normal that they’d recently confirmed that the two pages were part of a previously known math notebook from Lincoln’s childhood. It was found in the archives of Houghton Library at Harvard University, where it remains.
The book, known as a cyphering book in Lincoln’s day, is a sort math workbook in which Lincoln wrote math problems and their answers. It’s the oldest known Lincoln manuscript.