What can i make a high jump pit out of?

pleeease i need help! i really need a high jump pit. i only need the pit, because my dad's going to make the other parts. i've thought of mattresses, but i don't have access to about 4 or 5 which i would need. i heard hay would work, but i'm allergic to it. i couldn't use a pool either, because i don't have one, and i would need to wear sneakers while jumping. so what could i possibly use?|||I ride freestyle motorcross and just made a backflip pit filled with foam blocks... You could try your local sewing store depending on the size of your pit... if not check online! Good luck and happy jumping