《太平广记·卷十八·神仙十八》
忽见道旁有一块大石头，整个石头都透明铮亮，又圆又平，方圆六七亩大小。
忽道旁有一大石，表里洞澈，圆而砥平，周匝六七亩。
Suddenly, he saw a large rock at the side of the road; the stone was completely transparent and vibrantly glossy, perfectly round and flat, with a dimension of six or seven acres.