"Ten men, stripped of all their clothes, step into the vessel, and begin to tread down the floating mass [of grapes], working it also with their hands. This operation is repeated several times if the wine does not ferment rapidly enough. The reason...is that the bodily heat of the men aids the wine in its fermentation."

ewww...

Also, apparently these are some dangers of wine by treading: drowning (in grape pulp), and after a while, the grapes ferment and produce large quantities of carbon dioxide, and the treaders can be asphyxiated.

No worries mates, treading isn't a method widely-used anymore. *phew*. I know I'm relieved.