Mattress

The design consists of the features of shape, configuration and ornamentation applied to a mattress as illustrated in solid lines in the attached drawings.Drawings of the design are included wherein:FIGURE 1 is a front elevational view of the article to which the design is applied, namely, a mattress;FIGURE 2 is a rear elevational view thereof;FIGURE 3 is a left side elevational view thereof;FIGURE 4 is a right side elevational view thereof;FIGURE 5 is a top view thereof;FIGURE 6 is a bottom view thereof;FIGURE 7 is a perspective view thereof.