There have been a few new deveelopments at my family home since the last time I was here. One of them is the acquisition of a couple of handsome new teacups, made of glass. The things are so pretty, and, from a physical standpoint, so clever, that I’m honestly disappointed that I myself didn’t think of them. You see, they consist of two concentric glass shells with only air between. This, contrary to naive expectations about things made out of glass, is actually perfectly well-insulated for the very simple reason that the layer of air in between the two glasses is actually a considerable poorer conductor of heat than common ceramics.
It could be a bit cleverer though; the space between the layers of glass could be evacuated, but that would probably be prohibitively expensive.
EDIT: A reliable source has just informed me that these cups in fact include a permeable, gummy layer at the bottom which is permeable to air but not to liquid. More on this story as it develops.