Numerical digit
From India, the thriving trade between Islamic sultans and Africa carried the concept to Cairo. Arabic mathematicians extended the system to include decimal fractions, and Muḥammad ibn Mūsā al-Ḵwārizmī wrote an important work about it in the 9th  century. The modern Arabic numerals were introduced to Europe with the translation of this work in the 12th century in Spain and Leonardo of Pisa's "Liber Abaci" of 1201. In Europe, the complete Indian system with the zero was derived from the Arabs in the 12th century.
Watch 1505
The widespread network of the Muslim Caliphates interconnected with the world's known trade routes, mainly the Silk Road from China to the Caliphate of Cordoba and Al-Andalusian Spain, were not only the most important trade routes but also networks of knowledge transfer. The broad network made it necessary to have primarily navigation devices, such as astrolabes, which were introduced to Europe from Muslim Spain in the early 12th century. The Andalusian mathematician and astronomer Al-Muradi wrote the technological manuscript "Kitāb al-asrār fī natā'ij al-afkār" ("The Book of Secrets in the Results of Thoughts"). The manuscript provides information about a "Castle and Gazelle Clock" and many other forms of complicated clocks and ingenious devices.