Usually attributed to Ibn Sīnā [e.g. King (Survey B81, p. 49) but this is mainly from the section on "Natural Bodies" in the Rasā'il of the Ikhwān al-Ṣafāʾ (Risāla II in vol. 2, pp. 24-51 of the Beirut edition); partially translatated into Italian by Giorgio Scrimieri, *Testimonianze medievali e pensiero moderno*, Bari: Edizioni Levante, 1970, pp. 171-189 based on Cairo, DK hay'a 10. Has been edited by Maha Khidr (Cairo, 2006).