It was September 1738, and Benjamin Lay had walked 20 miles, subsisting on “acorns and peaches,” to reach the Quakers’ Philadelphia Yearly Meeting. Beneath his overcoat he wore a military uniform and a sword — both anathema to Quaker teachings. He also carried a hollowed-out book with a secret compartment, into which he had tucked a tied-off animal bladder filled with bright red pokeberry juice.