The post office has a good deal on shipping using one of their "flat rate" boxes. There's a 70# weight limit. The boxes are available in a couple of sizes, but there's one that's about 10 x 6 x 6 or so -- which'd nearly the right size for some heavy stuff like a lead brick, I'd think. Nancy gets bulk supplies for some of her artsy stuff this way -- and 40# costs the same as would 70# -- and also the same as 3# -- flat rate is $8.95. Check it out.