Kitab Al-Hiyal. The Book of Ingenious Devices.

‘ In the Kitab al-Hiyal, three brothers—Muhammad, Ahmad, and al-Hasan bin Musa ibn Shakir, known as the Banu Musa (“sons of Moses”) describe some 100 devices. Sons of a respected astronomer, the brothers were supported by Baghdad’s ruler al-Ma’mun and his successors. Among their other notable projects was an initiative to measure the circumference of the earth, accomplished by walking the distance on a marked route for a one-degree shift in altitude of the Pole Star (which they did at two locations for accuracy). They reported a circumference of 24,000 miles, only slightly less than the modern figure of 24,902 miles. Individually and together, they also published noted treatises on geometry and mathematics, timekeeping, the nature of speech, and other topics.
Written during a period characterised as a “golden age” of Islamic science, engineering, and medical discovery, along with linguistic, philosophical, and cultural advances, the Kitab al-Hiyal differs from scientific manuscripts of the era in its descriptions of useful and practical technologies. The term, “Islamic Golden Age” is of uncertain origin, but has been used widely since scholarship in the 1970s criticised long-standing Western perceptions of the Middle East and Asia as primitive or unscientific’. (Smithsonian Institute).