In a number of recent philosophical works, the concept of ontography has been raised to involve a revaluation of figurative and visual thinking against logico-conceptual thinking—i. e. a revaluation of a philosophical practice that supplements or departs from the traditional site of philosophy, language. This paper investigates the ontographic dimensions of Charles S. Peirce’s diagrammatology by focusing on his system of »existential graphs« as ontography avant la lettre.