Euler’s number, the number e, is a mathematical constant approximately equal to 2.71828. You encounter the number e in mathematics almost every day because it is the base of the natural logarithm, the limit of (1 + 1/n)n as n approaches infinity, and an expression that arises in the study of compound interest.

Z Proportions
Becca Hirsbrunner photographed this fabulously constructed Z proportions letter. Interestingly, every element but the diagonal bar can be rationalized.