《论衡·卷八·儒增篇》
人碰上水火的灾难，感到惶惑恐惧，抬东西搬东西，精力集中，加倍用心到极点，平常抬一块石头的也会加倍用力抬起二块石头来。
有水火之难，惶惑恐惧，举徙器物，精诚至矣，素举一石者，倍举二石。
When a man comes across the disasters of water and fire, feeling terrified and afraid, if he has to lift or move something, his strength and effort would be focused to the extreme, and a man who could normally lift a stone could possibly lift two stones with extra power.