Drug trial: Persian physician Avicenna, in The Canon of Medicine (1025), first described use of clinical trials for determining the efficacy of medical drugs and substances.[96] Double-entry bookkeeping system: Double-entry bookkeeping was pioneered in the Jewish community of the medieval Middle East.[97][98] Hyperbolic geometry: The theorems of Ibn al-Haytham (Alhacen), Omar Khayyám and Nasīr al-Dīn al-Tūsī on quadrilaterals were the first theorems on hyperbolic geometry.[99] Magnifying glass and convex lens: A convex lens used for forming a magnified image was described in the Book of Optics by Ibn al-Haytham in 1021.[100] Mechanical flywheel: The mechanical flywheel, used to smooth out the delivery of power from a driving device to a driven machine and, essentially, to allow lifting water from far greater depths (up to 200 metres), was first employed by Ibn Bassal (fl.