For thousands of years humans have transported heavy goods on their backs using a head held tump line. The loads a fit porter can carry are astonishing. Some can manage 100 kilos (220 pounds), which considering their own body size is incredible. These guys in Nepal can manage both heavy and awkward loads with ingenuity. Keep in mind that the coke bottles below are heavy glass (made to be washed and re-used many times), and are filled. Just one wooden tray would be a load for most of us. I've seen these porters pack in refridgerators, heavy lumber, furniture, and mother-in-laws. These photos are by Jeff Greenwald.