Coffee = Theorems
This elegant series of coffee stains on mathematical jottings brings new meaning to mathematician Alfréd Rényi's comment that "a mathematician is a machine for turning coffee into theorems."
This particular coffee-drinking mathematician fills hundreds of pieces of scratch paper with his notations in the process of creating his theorems. The scratch paper is then used to drain coffee filters. If coffee hadn't been invented, these theorems might not exist.