The legend of a person's seven-year journey to attain immortality by drilling through a five-foot stone slab, guided by Supreme Lord Laozi.
A person entered Jiaoshan to study Dao for seven years. The Supreme Lord Laozi gave him a wooden drill and instructed him to bore through a slab of stone five feet thick. Supreme Lord Laozi said, “Once you bore through this slab of stone, you will attain the Dao and become an immortal.” This person drilled for a total of forty years, eventually boring through the slab of stone, and as a result, he obtained the secret formula for cultivating immortality elixirs.
《焦山老君》
有人入焦山七年，老君与之木钻，使穿一盘石，石厚五尺。曰：“此石穿，当得道。”积四十年，石穿，遂得神仙丹诀。