In 1206, Al-Jazari invented programmable automata/robots. He described four automaton musicians, including two drummers operated by a programmable drum machine, where the drummer could be made to play different rhythms and different drum patterns. The castle clock, a hydropowered mechanical astronomical clock invented by Al-Jazari, was an early programmable analog computer. In the Ottoman Empire, a practical impulse steam turbine was invented in 1551 by Taqi ad-Din Muhammad ibn Ma'ruf in Ottoman Egypt. He described a method for rotating a spit by means of a jet of steam playing on rotary vanes around the periphery of a wheel. Known as a steam jack, a similar device for rotating a spit was also later described by John Wilkins in 1648. Medieval Europe While medieval technology has been long depicted as a step backwards in the evolution of Western technology, a generation of medievalists (like the American historian of science Lynn White) stressed from the 1940s onwards the innovative character of many medieval techniques. Genuine medieval contributions include for example mechanical clocks, spectacles and vertical windmills. Medieval ingenuity was also displayed in the invention of seemingly inconspicuous items like the watermark or the functional button. In navigation, the foundation to the subsequent age of exploration was laid by the introduction of pintle-and-gudgeon rudders, lateen sails, the dry compass, the horseshoe and the astrolabe. Significant advances were also made in military technology with the development of plate armour, steel crossbows and cannon. The Middle Ages are perhaps best known for their architectural heritage: While the invention of the rib vault and pointed arch gave rise to the high rising Gothic style, the ubiquitous medieval fortifications gave the era the almost proverbial title of the 'age of castles'. Papermaking, a 2nd-century Chinese technology, was carried to the Middle East when a group of Chinese papermakers were captured in the 8th century. Papermaking technology was spread to Europe by the Umayyad conquest of Hispania. A paper mill was established in Sicily in the 12th century. In Europe the fiber to make pulp for making paper was obtained from linen and cotton rags. Lynn Townsend White Jr. credited the spinning wheel with increasing the supply of rags, which led to cheap paper, which was a factor in the development of printing. Renaissance technology Before the development of modern engineering, mathematics was used by artisans and craftsmen, such as millwrights, clock makers, instrument makers and surveyors. Aside