Max Planck (1858–1947) German theoretical physicist
Letter to Robert W. Wood (October 7, 1931) in Archive for the History of Quantum Physics, Microfilm 66, 5, as cited in Thomas S. Kuhn, Black-Body Theory and the Quantum Discontinuity, 1894–1912 (1978) pp. 132, 288. Translation of the entire letter, which is follow above is in Armin Hermann, Frühgeschiche der Quantentheorie (1899–1913) Mosbach/Baden: Physik Verlag (1969), transl. Claude W. Nash, p. 23 of the translation; and also in M. S. Longair,Theoretical Concepts in Physics(Cambridge and NewYork: Cambridge University Press, 1984), ch. 6–12, p. 222. All as quoted/cited by Clayton A. Gearhart, "Planck, the Quantum, and the Historians" http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.613.4262&rep=rep1&type=pdf, Physics in Perspective, 4 (2002) 170-215.