Where do you get 1 cubic meter? Anyone talking about grains in such a small area without referencing volumetric differences between grains, is making up measure

Where do you get 1 cubic meter? Anyone talking about grains in such a small area without referencing volumetric differences between grains, is making up measurements. There are multiple order differences between sand types. http://www.sandatlas.org/brain-games-with-sand-grains/ http://www.sandatlas.org/brain-games-with-sand-grains/