I stumbled across this series of images recently on the V&A website:
It's a lovely mantua, crafted of (probable) Spitalfields silk woven in 1733-34. The dress was constructed a few years later. It's fascinating to see the economical use of the textile in the construction of the garment and careful geometry at play in the gown while it is in repose (undraped)...
...And how it is transformed by artful, expert draping on the human form. I've read several times that mantua draping was an art, and that particularly skilled ladies maids were highly desired for their ability to drape their mistresses' gowns.
I guess I understand now.