Mnaseas is reckoned to have been a pupil of a scholar who was chief librarian at what library?
Eratosthenes Eratosthenes of Cyrene ( ; Greek: Ἐρατοσθένης ὁ Κυρηναῖος , ] ;  – ) was a Greek mathematician, geographer, poet, astronomer, and music theorist. He was a man of learning, becoming the chief librarian at the Library of Alexandria. He invented the discipline of geography, including the terminology used today.
Al-Tirmidhi Abū ‘Īsá Muḥammad ibn ‛Īsá as-Sulamī aḍ-Ḍarīr al-Būghī at-Tirmidhī (Arabic: أبو عيسى محمد بن عيسى السلمي الضرير البوغي الترمذي‎ ‎ ; Persian: ‎ ‎ , "Termezī"; 824 – 9 October 892), often referred to as Imām at-Termezī/Tirmidhī, was a Persian Islamic scholar and collector of hadith who wrote "al-Jami` as-Sahih" (known as "Jami` at-Tirmidhi"), one of the six canonical hadith compilations in Sunni Islam. He also wrote "Shama'il Muhammadiyah" (popularly known as "Shama'il at-Tirmidhi"), a compilation of hadiths concerning the person and character of the Islamic prophet, Muhammad. At-Tirmidhi was also well versed in Arabic grammar, favoring the school of Kufa over Basra due to the former's preservation of Arabic poetry as a primary source.