This is actually a compilation from the Rasā'il of the Ikhwān al-Ṣafā’, mainly from Risāla II on "Natural Bodies" (vol. 2, pp. 24-51); partially translatated into Italian by Giorgio Scrimieri, *Testimonianze medievali e pensiero moderno*, Bari: Edizioni Levante, 1970, pp. 171-189 based on DK, hay'a 10