The bustle, by extending the body, became a point of demarcation for the back of the waist. By enlarging the derriere visually, the bustle became a foil for the constricted waist in profile. Bustles were silk-floss, cotton, or feather down-filled. Small ones could be found sewn into Empire gowns; more prominent ones were used in the 1870s and 1880s and had an ingenious range of configurations and materials, including wire coil, rattan, and horsehair.
The Metropolitan Museum of Art. "Waist Not," March 30, 1994–August 21, 1994.