A 1850 circa ballgown
Not a costume, but an original victorian dress [link]
and headdress [link]
To answer to who, looking at this picture, claimed that historical dresses should not be worn, I would like to clarify that... I agree.
I have more that 1200 antique clothing items, including almost 200 complete dresses from 1780 to 1930. They are stored flat, in acid free paper, away from light, dust and insects. I never wear them, I collect them only for their historical value.
But for one time I wanted to try the thrill.
To prevent damages I wore it inside (no direct sunlight), with a T-shirt underneath so it didn't touch my body skin, and for no more than 15 minutes. And I choose a dress my size so it wasn't stressed by stretching.
You can see my collection here: [link]