I agree with Neil that an egg would look odd next to a teapot. How about a teabag next to a teapot or a mug, a common flower next to a vase, an apple next to a serving bowl, an egg next to a batter bowl.... something in context and easily recognizable.
Min's got the right idea!
I live in Australia so what size is an American penny?? We use metric measurement so how much is 6oz? Only the US, UK and some Chinese business still use imperial measurement........so this could be costing you sales! It might prove easier to click on another offering rather than sit there pouring water into measuring jug or doing maths conversions to work out your sizes.
Etsy, ArtFire and all the online platforms are international sites so to maximise sales potential you'd need to list in metric and imperial and put something as a size indicator that doesn't rely on language but is recognisable all over the world. For example the hen's egg....a hen's egg in a bowl is a pretty recognisable image in most kitchens around the world, if it's big in the bowl then the bowl is likely small, if the egg is small then the bowl likely large and so the measurements are more easily visualised.
Yes, it would take some thought I guess but it comes down to whether a person wants international sales or domestic only....both are good.