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.
Orion of Thebes Orion of Thebes (died c. 460s) was a 5th-century grammarian of Thebes (Egypt), the teacher of Proclus the neo-Platonist, and of Eudocia, the wife of Emperor Theodosius II. He taught at Alexandria, Caesarea in Cappadocia and Constantinople. He was the author of a partly extant etymological Lexicon (ed. F. W. Sturz, 1820), largely used by the compilers of the "Etymologicum Magnum", the "Etymologicum Gudianum" and other similar works; a collection of maxims in three books, addressed to Eudocia, also ascribed to him by Suidas, still exists in a Warsaw manuscript.