I didn't have a tape measure with me in the Glencoe Visitor Centre but from measuring bags of sugar at home I estimate the box to be 35cm on each side. That would give a volume of 43 x 10^3 cubic centimetres and a density of snow of 28 x 10^3/43 x 10^3 = 0.65 grams per cubic centimetre. This would make it firn, which seems unlikely. But if the box is actually 40cm on each side, density comes down to 0.44 g/cm^3 which is almost down to the density of wind-packed snow. I should have taken the tape measure!
