How Euler Did It
The latest book in the MAA Tercentenary Euler Celebration series collects 40 online columns from Ed Sandifer's "How Euler Did It". One of these gives the results of a poll of Euler's most important results, such as the Konigsberg bridge problem, the polyhedral formula V – E + F = 2, and of course eπi + 1 = 0, which has also figured on lists of the most beautiful equations.
You'll have to check the continuing online column to find out why "Euler" is in the Euler Identity.
How Euler Did It by C. Edward Sandifer. The MAA tercentenary Euler celebration v. 3. Washington, DC: Mathematical Association of America, 2007. Mathematics Library QA29.E8 S264 Link to MNCAT record