Walter R. asked his math assistance Thomas Harret how many cannons balls could be stacked. But Thomas went much farther with it because it was easy. So he looked at the study of close packing and also rebirth atomic theory. So he asked Johannes Kepler about it and because he was not a mathematician he didn't want to do much about it. But still he looked into it. Finally in 1611 Kepler used a watered down version of atomism. Describes the face centered cubic packing and said this type of packing is he tightest possible meaning in no other way could more pellets fit in the same container that became know as Kepler's conjecture. He stated that density can't exceed pi/sqrt(18)=0.74048. So that means that you can't fill more then 74% of a container.