Mattress

FIG. 1 is a front perspective view of a mattress, illustrating our new design;

FIG. 2 is a front elevation view thereof;

FIG. 3 is a rear elevation view thereof;

FIG. 4 is a left side view thereof;

FIG. 5 is a right side view thereof;

FIG. 6 is a top view thereof; and,

FIG. 7 is a bottom view thereof.

The broken lines of even length in the drawings illustrate portions of a mattress that form no part of the claimed design. The broken lines of uneven length illustrate the boundary of the claimed design and form no part thereof.