„Let there be in every material particle several material points charged with electricity, of which, however, only one be movable, and have the charge e and the mass μ.“
— Hendrik Lorentz
As quoted by Walter Kaufmann, "The Development of the Electron Idea" (Nov. 8, 1901) The Electrician [https://books.google.com/books?id=owxRAAAAYAAJ Vol. 48] pp. 95-97. Lecture delivered before the 73rd Naturforscher Versammlung at Hamburg. From the Physikalische Zeitshrift, of October 1, 1901.