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"