Beatrice Warde’s metaphor of “the crystal goblet”

What does Beatrice Warde’s metaphor of “the crystal goblet” mean? How does she think typography should work? Did the kind of typographic design described by certain people featured in Helvetica remind you of Warde’s argument? Which designers and why? In comparison (or contrast) with Warde, what is Weingart’s take on typography? How do his ideas or opinions relate to those of the designers featured in Helvetica?