They can be found in the Library's collections of incunabula (early printed books 1450-1500). The Rare Books and Special Collections Division has the largest collection of incunabula in the western hemisphere. The majority of these books are in Latin. To view these items, you must visit the aforementioned reading room.
Neo-Latin texts can be found in various editions in the general collections. These can be found by searching in the Library's online catalog. You can search by title author, keyword, subject heading, etc. Titles can be searched in English, Latin, or any other language.
Regarding subject headings in the online catalog, here are a few to get you started: