If it is necessary, even the impossible is possible in overloading vehicles several times beyond the normal level of operation. Like transporting a car on a bicycle. Like ants, people in Third World countries carry objects several times larger and heavier than themselves with rudimentary means.
Another thing, which is very dangerous and often deadly, is the overcrowding of trains and boats. When even the last square-centimeter of standing room is choke full, a logical place to get on the train anyway is the roof.