Historical information
Smoking caps are caps worn by men while smoking to stop the hair from smelling of smoke. They also kept the head warm. They were popular in the period 1840-1880, usually worn by gentlemen in the privacy of their home. They are similar to the smoking jacket, though their use, even in Victorian times, was not necessarily as widespread.
Source: www.wikipedia.org
Physical description
Smoking cap. Embroidered net, silver-grey silk thread. Lining mushroom-coloured. Silky material stiffened with cardboard.