I have to admit that I'm generally a sceptic when it comes to private revelations and visions of Our Lady. I accept that they do occasionally occur, but an awful lot of the ones I get sent or read about seem to either state the bleeding obvious (like we're in the end times, repent) or include some rather bizarre elements.
The ones that do seem to make sense (to me at least) are where Our Lady is seeking the institution of some particular devotion, or helping along some development of doctrine. Elizabeth of Schonau's vision relating to the Assumption, which she received around 1157, is of the latter category.
Elizabeth was a Benedictine, and a friend of Hildegarde von Bingen.
On the octave day of the Assumption she fell into an ecstasy at mass, and Our Lady appeared to her:
"...following the advice of one of our superiors, I asked her:" My benevolent Lady, may it please you to make known to us whether you were assumed into heaven in spirit only or also in the flesh?" I mentioned this because, as they say, there is uncertainty about it in the books the Fathers wrote."
Our Lady initially refused to answer the question, but a year later, Elizabeth had a vision of the actual Assumption itself, an got an explanation of it which stated that Our Lady was physically resurrected after her death (a position which goes slightly further than defined doctrine on this topic which simply insists that she was assumed body and soul into heaven but is silent on whether she actually died first).
Elizabeth seems to have been given lists of questions to ask by eager theologians, and took the opportunity when she could!
Interestingly, according to the vision, Our Lady's Assumption actually occurred forty days after her death (September 23).