I remember reading about the first mountainbikes being balloon tyre bikes with drum brakes. They often had reinforced forks and larger drums fitted.
The drums were used with larger motorcycle levers that provided more leverage (regular short-pull levers nor direct pull work all that well).
One of those with fat tyres and some fenders would work great in hilly areas.
Further reading:
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The Hippie Daredevils Who Were Just Crazy Enough to Invent Mountain Biking - Collectorsweekly.com
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Were drum brakes ever fitted to a stock MTB? - Bikeforums.net @
Airburst
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Clunkers.net a history of mountainbikes