This may or may not be the correct forum to ask this, but let's ask it anyway. I am looking for historical information on density. It is so that densities can not be added lineary: A material containing 10% of material 1 and 90% of material 2 will not have a density of 10% * the density of material 1 + 90% * the density of material 2. I'd like to know who was the first that realized this. (any other historical information on density is also welcome).