Italian dealer in Hebrew and other ancient manuscripts; flourished at the beginning of the fourteenth century. He spent seven years in Toledo, searching successfully for Arabic and Hebrew books, and was able to circulate among the young students of Perugia a catalogue of eighty Hebrew and Arabic manuscripts.Immanuel de Romi and his friends, on one occasion, took advantage of Aaron's absence from home, broke open his book-cases, hastily copied some manuscripts, and Immanuel added insult to the harm done by writing, in the form of a letter, a bitter satire on Aaron.