Since we're doing math here, I'll point out that the 4 bases do not quite form a perfect 90-foot square. Home plate is located in fair territory inside the first base line and the third base line, with the point marking the corner of a 90-foot square. First base and third base are positioned such that the corner of the base toward the outfield along each foul line is 90 feet from the corner of home plate. Second base, however, is positioned with the center of the base located at the corner of the square. So home plate, first base and third base are positioned entirely inside the 90-foot square, but only the quarter of second base closest to home plate is within the square. Why should second base be different? Only the writer(s) of the rule knew, and he/she/they are no longer with us to answer.