The Alberti Grid T-shirt

In music theory, the difference between two notes on a scale is called an interval, and according to the Italian artist, architect and author Leon Battista Alberti, the intervals between harmonious notes could be visually harmonious as well, when used as ratios in composition. His method, known as Albertism, is one of the most cryptic and varied composition methods used in art history, its rhythms interpreted differently by each artist that used it. While it may look esoteric in isolation, you've probably seen this composition method at work, in Sandro Botticelli's most famous artwork, The Birth of Venus.