The box spring base was upholstered various methods. There may be a simple waterfall dropoff or a more complicated cantilever fashion.
The "box spring" beds were originally hybrid specialty sleep products that used woven wires and spiral springs. The spiral springs helped to prevent sagging.
As can be discovered by comparing patents and advertising developmentsin the 1860s-1890s, the box spring was originally in use as an under support for a cotton or hair stuffed mattress. As the creativity improved, it was discovered that the box spring could be comfortable in itself. This is the period where the woven wire mattress, the box spring mattress, the box spring bed, and the mattress shared technology improvements. It was not until the first quarter of the 20th Century that our current box spring and mattress model was really developed.
Bushnell's patent is often cited as the first innerspring mattress. As can be seen in viewing it, there is a similarity to our current "open coil" type mattress, but Bushnell was only improving on the bed bottom product.
It is suggested that you also check out the section on BED BOTTOMS and WOVEN WIRES.
Premium box spring beds were constructed so that the bottom portion of the box spring would rest on iron rails hooked or connected to the metal or brass "headboard" and "footboard" or structures. (These beds could also be fully wood construction). The edges would suspend out in a cantileverd design. Some companies called this a Biltmore style though many other names were used. The original use of spiral springs was in the box spring bed base; the cotton or hair stuffed mattress was used on top. It was only in the 20th Century that springs were put into mattresses.