Here is an account from 1852 of a voyage from San Francisco to New York by way of Panama and Jamaica. While in Jamaica, the ship took on a load of coal in Kingston. There is a description of about 50 men and women carrying coal in tubs on their heads and marching back and forth to load the ship and singing "an old plantation song" the whole time. It is the last paragraph just above the heading "Again on the deep":

http://cdnc.ucr.edu/newsucr/cgi-bin/newsucr?a=d&cl=search&d=SDU18921020.2.28&srpos=11&e=-------en-logical-20--1-byDA---capstan+s