I had heard a similar expression stating the "the perfect breast fits in a champagne glass." But is that a reference to the shallow, wide type or the narrow, fluted type?
I'm not sure I want to see boobs fitting the latter description. :-]
Shallow wide type is not a champagne glass. It's cognac/brandy, or some wines. Something that's upposed to breathe. Champagne isn't supposed to breathe, because all the bubbles go away, so it's the narrow glass.
Also, as a French acquaintance of mine recently informed me, it's a figure of speech. The saying goes, "More wine than what fills the glass is a waste," and refers to breast size, not shape.
He chuckled and agreed with me when I said, "In that case, I'd prefer a bigger glass."