I don't recall what is the current stage of consensus regarding Wikisource subpages on Wikidata, but because while playing "The Game" [1] I keep getting this kind of item (mostly from es.wikisource), I've managed a way to at least track those stuff [2]

I didn't did an exhaustive search for such items and I keep finding new, but at this momment it returns 2k of items.

[1] - https://tools.wmflabs.org/wikidata-game/

[2] - http://tools.wmflabs.org/wikidata-todo/autolist.html?q=CLAIM%5B31%3A17152355%5D