A mathematician who is not somehow a poet will never be a complete mathematician. Conversely, the lyricist Oswald Egger conducts fundamental research into the interactions between mathematics and poetry: he understands both as related modes of thought and proposes in his essays, "with cheerful seriousness," the connection from children's games to pattern formations in geometry and text. The history of ideas unfolds both abruptly and steadily, and this book makes the path of thought comprehensible: from the wonderhorn of folk songs to the inner metrics of topological spaces in Riemannian geometry. Egger does not shy away from complex mathematical questions; he takes them at their word. He addresses these in the tradition of Arno Schmidt's "reciprocal radii" or Edgar Allan Poe's "Eureka.".