re: Burial urn

The above dimensions of the cardboard box the ashes come in sounds about right for the two relatives I know that have been cremated but their body sizes were pretty small by the time they died (<120 lbs).  Someone larger might require larger box so I would estimate based upon the weight.  

I thought about making an urn for my eventual ashes but I finally just told my family to dump my ashes on the compost pile and later spread the compost in my garden to fertilize the flowers once fully composted.  If I could, I would just have myself composted as to not waste the energy to cremate and also so that the energy tied up in my body would stay on the planet.  When you are cremated, the energy from your body escapes into space and is lost forever rather than being recycled into new living things.