They told her how, upon St. Agnes' Eve, Young virgins might have visions of delight, And soft adorings from their loves receive Upon the honey'd middle of the night, If ceremonies due they did aright; As, supperless to bed they must retire, And couch supine their beauties, lily white; Nor look behind, nor sideways, but require Of heaven with upward eyes for all that they desire.
These old ladies have been telling our young Lady that, on St. Agnes' Eve, virgin girls can have visions of their loves (future husbands, as the myth actually goes) at midnight if they follow a few rituals.
What rituals might these be? We get a list: they have to go to bed without dinner, totally undress right before bed (if you were wondering what "supine beauties, lily white" referred to, it's the girls' naked bodies—"supine" means lying face-up), and when they're actually going to bed, they can't look around them; they can only look upwards and hope heaven gives them a preview of their future husbands. This would come at a figuratively sweet time ("the honey'd middle of the night").
Personally, we think the idea of getting a teaser trailer of your future beloved sounds like a cool idea.