Chemises - essential for your period impression, I also found out when I was reenacting, that they were very comfortable to sleep in during the summer. So now I wear them as a night gown during the summer months. Can be worn on or off the shoulders.
Here is a chart of approx measurements:
Size Shoulders Length
S 12-3/4" 42"
M 14" 42"
L 15" 42"
XL 16-3/4" 43"
2XL 17-1/2" 43"