Theodor Spieker
Theodor Spieker was a German mathematician, a teacher at a gymnasium in Potsdam.
Spieker's geometry textbook Lehrbuch der ebenen Geometrie mit Übungs-Aufgaben für höhere Lehranstalten was republished in many editions. A copy of this textbook was given to Albert Einstein by his tutor when Einstein was twelve, and quickly led Einstein to become interested in higher mathematics.
Spieker is the namesake of the Spieker circle of a triangle and the Spieker center.
