There are many interesting things in the cyphering books that George Washington compiled as a teenager: His study of decimal arithmetic is straightforward, but understanding some of the errors he made can be a fun. He had a technique for partitioning a plot of land into two equal pieces, but it was wrong --- and so was his source. Some things are hard to understand for time has passed them by. For example, his pre-Eulerian trigonometry is a mystery today, so we shall elucidate it. We shall present some pages of his cyphering books that the Library of Congress did not digitize because they were at Cornell, Dartmouth and the Historical Society of Pennsylvania.