Earl of Sandwich Doing the Math
The book asked the Big Question: "Why is it so much better to slice a sandwich diagonally than straight across?
Oddly, two of the answers involved mathematics. First, the hypotenuse creates a geometry that "reveals maximum meat." Using the Pythagorean Theorem on a 5"-square piece of bread, the authors showed that the difference is 5 inches (halved midpoint to midpoint) vs. 7 inches-plus (the diagonal)... making "better presentation."
Second, mouth action... as described aptly in Nicholson Baker's novel The Mezzanine: "In the case of rectangular toast you had to angle the shape into your mouth, as you angle a big dresser through a hall doorway: you had to catch one corner of your mouth with one corner of the toast and then carefully turn the toast, drawing the mouth open with it so that its other edge could clear; only then did you chomp down."
Strange...in the time it took to describe and justify the best cut, I could have eaten several sandwiches! But, it provides unexpected evidence that math lurks everywhere!
E.S. adds a ractical view: "Diagonally is better if you’re eating it right away, but if you’re packing a picnic or sack lunch, cutting it into rectangles packs away much more neatly with less potential smushing."
Source: J. Achenbach, Why Things Are (Vol. II), 1993, pp. 198-199