Juergen found this today:

Big Wheels in Canadian Cycling
posed for this 1898 photo before pedaling themselves and their gargantuan trike to the next town. It literally took six men and a boy to propel the contraption, whose rear wheels measured 14 feet in diameter. In wet weather, it was reported, the trike was a holy terror, with a marked tendency to skid out of control on its smooth balloon tires.

(originally from http://www.hemmings.com/features/oddies/oddies.cfm?id=123 but it’s since disappeared.)