How do we most efficiently farm treasure maps?
I know they come from "containers", but is there any data on which type of containers drop treasure maps the most?
I specifically want Summerset treasure maps for the book furnishing that drops from them, but I don't think there's a way to try to get more of one type of treasure map. So any information on how to obtain piles of treasure maps helps.
I used bunches of Summerset treasure maps in search of the book furnishing. Only to find out that we needed to have read certain lorebooks first

I'm giving it another shot this upcoming event, but I'm all out of Summerset treasure maps. Any help is appreciated.