In response to a reader query, this article traces the origins of the ionic-radius ratio rules and their incorrect attribution to Linus Pauling in the chemical literature and to Victor Goldschmidt in the geochemical literature. In actual fact, the ionic-radius ratio rules were first proposed within the context of the coordination chemistry literature by the Austrian chemist, Gustav F. Huttig, in a brief note published in 1920 in which he reported the R[subscript -]/R[subscript +] ratio for possible geometries corresponding to coordination numbers of 2, 3, 4, 5, 6, 8, 12, and 20. Two years later the German chemist, Alfred Magnus, gave a more detailed treatment explicitly linked to Walther Kossel's recently proposed electrostatic screening theory of complex ion formation and also included values for various alternative coordination geometries, such as square planar versus tetrahedral and hexagonal planar versus octahedral. In 1923, Huttig's original results were cited by Max Lembert in a discussion of the structures of complex hydrates, and the following year they were incorporated into the second edition of Rudolf Weinland's textbook, "Einfuhrung in die Chemie der Komplexverbindungen." In a series of papers published in 1925 by Rudolf Straubel and Huttig, the rules were further linked to the concept of packing efficiency.