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.
Trosius Aper Trosius Aper was a grammarian of ancient Rome who served as one of two Latin tutors for the Roman emperor Marcus Aurelius, along with Tuticius Proculus. He was from Pola (modern Pula) in Istria, and was assigned to Aurelius as a tutor around 132 or 133. As a tutor, Aper would have Aurelius read classical works out loud, and memorize them, later commenting on stylistic matters, and drawing philosophical lessons from the text for his pupil.