Nasir al-Din al-Tusi

I first came across Muhammad ibn Muhammad ibn al-Hasan al-Tūsī ‎‎ (18 February 1201 – 26 June 1274) in Dr Stephen Skinner’s work Terrestrial Astrology ‘Divination by Geomancy’

The Muslim scholar Ibn Khaldun (1332–1406) considered Tusi to be the greatest of the later Persian scholars.  As the armies of Genghis Khan swept his homeland, he was employed by the Nizari Ismaili state and made his most important contributions in science during this time when he was moving from one stronghold to another. He was captured after the invasion of Alamut Castle by the Mongol forces.

Born in Savah, or in Tus, Khurasan, Al-Tusi was also a philospher, astronomer and physician, who wrote in both Arabic and his native language. His devotion to systematic scientific inquiry led to him being dubbed ‘al-Muhaqqiq’, the investigator. He was kidnapped at an early age by the Isma’ili governor of Quhistan, and sent to Alamut, where he remained, if not a prisoner at least an unwilling guest, until its capture by the Mongols in 1256.

When the Assassins quietly handed over their stronghold, Al-Tusi entered the service of the grateful Mongol chief, taking with him much of the library and knowledge of the Assassins.  He remained in Mongol service, becoming a wazir and obtaining increasing influence over the Mongol chief Hulagu Khan by his astrological knowledge.

Soon Hulagu did not dare to undertake anything without his astrologer’s advice, and Al-Tusi was finally appointed administrator of the property revenues which he may have used to help build and endow the observatory and library of Maragha, where he resided from 1259 until almost the end of his life in 1274.

Dr Stephen Skinner _ Terrestrial Astrology ‘Divination by Geomancy’

Maragha Obs

The construction of the Maragha Observatory commenced in 1259 under the patronage of Genghis Khan’s grandson Hūlāgū. Its director was Nasīr al-Dīn Tūsī (1201–1274), an eminent Persian mathematician, astronomer and philosopher whose reputation spread as far as China and whom Hūlāgū had appointed as one of his advisors. The observatory was in fact a scientific institute, with a main building for the observational equipment, some auxiliary buildings, and accommodation quarters. In the observatory, there was a library which is said to have contained about 400,000 volumes. A team of astronomers, most of whom were invited from different parts of the Islamic world, were responsible for the design and construction of the astronomical instruments, as well as for conducting observations and performing calculations.

According to a text written by Mu’ayyad al-Dīn al-‘Urdī (d. 1266), one of the chief astronomers and instrument designers of the observatory, its astronomical equipment included a mural quadrant with a radius of about 40m, a solstitial armilla, an azimuth ring, a parallactic ruler (triquetrum), and an armillary sphere with a radius of about 160cm.

After the death of Nasīr al-Dīn Tūsī in 1274, the Maragha observatory was supervised by his son and remained active until the end of the 13th century. However, following the death of Hūlāgū in 1265 and his son Abāqā in 1282, it lost its powerful patrons and had become inactive by the beginning of the 14th century. Despite this, we have reports that Ghāzān Khān, who reigned from 1295 to 1304, visited the Maragha Observatory several times, probably using it as a model for his own observatory in Tabriz

THE GREAT Sextant (astronomical) AT THE MARAGHA OBSERVATORY- 1259 EC Iran / Azarbayejan-e Sharqi / Maragheh

Four hundred thousand volumes is a fair collection, a Wikipedia source mentions forty thousand.

The building, which no doubt served as a citadel as well, enclosed a space of 340 by 135 meters, and the foundations of the walls were 13 to 2 meters in thickness. The observatory was constructed in the thirteenth century and was said to house a staff of at least ten astronomers and a librarian who was in charge of the library which allegedly contained over 40,000 books. This observatory was one of the most prestigious during the medieval times in the Islamic Empire during the golden age of Islamic science.

Maragheh From Wikipedia

Anybody else wondering how much of the library of the Assassins ended up in the library of Maragha?