That was also true of torture, flogging, stocks, breaking on the wheel, burning at the stake, the heretic's fork, knee splitters, the rack, thumbscrews, and the other various sadistic forms of punishment that every European civilization routinely used on its prisoners before they were condemned as barbaric and banned.
They were not regarded as "cruel and unusual" because they were uncommon, but because they went against contemporary ideas of fairness, civility and efficacy as legal tools.
I would argue that the threat of 35 or 50 years in a federal prison for a victimless act of civil disobedience is similarly "cruel and unusual" against today's ideas of fairness, civility and efficacy.