Plan and cross-section of the Sisyphus ramp.

Davis's crew had constructed a scaled-down replica of the steepest ramp still existing on Easter Island, a daunting 1:4 or 25 percent slope. His team also assembled several large blocks of white marble from which to select a load, depending on how many people turned out to help move it. See documentary Easter Island (2000).

Source: http://www.pbs.org/wgbh/nova/lostempires/easter/vince.html