(EN) R. Rashed, The Celestial Kinematics of Ibn al-Haytham, in Arabic Sciences and Philosophy: A Historical Journal, vol. 17, n. 1, Cambridge University Press, 2007, pp. 7–55 [19], DOI:10.1017/S0957423907000355.
«In his optics the smallest parts of light, as he calls them, retain only properties that can be treated by geometry and verified by experiment; they lack all sensible qualities except energy.»