Volume Containing a Solid Foot

Puzzle

 * Mathematicians affirm that of all bodies contained under the same superficies, a sphere is the most capacious;
 * but they have never considered the amazing capaciousness of a body,
 * the name of which is now required,
 * of which it may be truly affirmed that supposing:
 * its greatest length $9$ inches,
 * greatest breadth $4$ inches,
 * and greatest depth $3$ inches,
 * yet under these dimensions it contains a solid foot.

Solution
A shoe.