The design consists of the features of shape, ornament, pattern and configuration of the MATTRESS WITH HORIZONTAL HANDLES. The portions shown in stippled lines do not form part of the design. In the drawings: FIGURE 1 is a perspective view of a first variant of the MATTRESS WITH HORIZONTAL HANDLES according to the design; FIGURE 2 is a side elevation view thereof, the opposed side view being identical; FIGURE 3 is an end view thereof, the opposed end view being identical; FIGURE 4 is a top plan view thereof; FIGURE 5 is a bottom plan view thereof; FIGURE 6 is a perspective view of a second variant of the MATTRESS WITH HORIZONTAL HANDLES according to the design; FIGURE 7 is a side elevation view of the second variant, the opposed side view being identical; FIGURE 8 is an end view of the second variant, the opposed end view being identical; FIGURE 9 is a top plan view of the second variant; FIGURE 10 is a bottom plan view of the second variant; FIGURE 11 is a perspective view of a third variant of the MATTRESS WITH HORIZONTAL HANDLES according to the design; FIGURE 12 is a side elevation view of the third variant, the opposed side view being identical; FIGURE 13 is an end view of the third variant, the opposed end view being identical; FIGURE 14 is a top plan view of the third variant; FIGURE 15 is a bottom plan view of the third variant; FIGURE 16 is a perspective view of a fourth variant of the MATTRESS WITH HORIZONTAL HANDLES according to the design; FIGURE 17 is a side elevation view of the fourth variant, the opposed side view being identical; FIGURE 18 is an end view of the fourth variant, the opposed end view being identical; FIGURE 19 is a top plan view of the fourth variant; FIGURE 20 is a bottom plan view of the fourth variant; FIGURE 21 is a perspective view of a fifth variant of the MATTRESS WITH HORIZONTAL HANDLES according to the design; FIGURE 22 is a side elevation view of the fifth variant, the opposed side view being identical; FIGURE 23 is an end view of the fifth variant, the opposed end view being identical; FIGURE 24 is a top plan view of the fifth variant; FIGURE 25 is a bottom plan view of the fifth variant; FIGURE 26 is a perspective view of a sixth variant of the MATTRESS WITH HORIZONTAL HANDLES according to the design; FIGURE 27 is a side elevation view of the sixth variant, the opposed side view being identical; FIGURE 28 is an end view of the sixth variant, the opposed end view being identical; FIGURE 29 is a top plan view of the sixth variant; FIGURE 30 is a bottom plan view of the sixth variant; FIGURE 31 is a perspective view of a seventh variant of the MATTRESS WITH HORIZONTAL HANDLES according to the design; FIGURE 32 is a side elevation view of the seventh variant, the opposed side view being identical; FIGURE 33 is an end view of the seventh variant, the opposed end view being identical; FIGURE 34 is a top plan view of the seventh variant; FIGURE 35 is a bottom plan view of the seventh variant; FIGURE 36 is a perspective view of an eighth variant of the MATTRESS WITH HORIZONTAL HANDLES according to the design; FIGURE 37 is a side elevation view of the eighth variant, the opposed side view being identical; FIGURE 38 is an end view of the eighth variant, the opposed end view being identical; FIGURE 39 is a top plan view of the eighth variant; and FIGURE 40 is a bottom plan view of the eighth variant.