The image above shows the harvesting of salt from the Cargill salt ponds on the southern end of Bonaire, WI.  

There are just two employees - one operating the Caterpillar dozer and one driving the Caterpillar belly dump.  The belly dump is filled to overflowing in just a few minutes.   Much of this salt gets shipped by sea to the icy parts of North America for road de-icing.   

The image below is a copy of a black and white photo (the original of which is in a museum on Bonaire - not sure of the date) showing two laborers using picks to break the salt crust on the same salt ponds, while a third laborer lifts the broken chunks of salt onto a wheel barrow.  

All human energy - no Diesel fuel!