返老还童 — “To recover one's youth”

Legend has it that Liu An, from his youth, was deeply fascinated by the path to immortality. After being granted the title of King of Huainan, he dedicated himself even more to this pursuit, sending people far and wide to inquire about rejuvenation techniques and search for elixirs of immortality.

One day, eight old men with white hair and silver beards suddenly sought an audience, claiming they possessed methods to reverse aging and wished to offer the elixir of immortality to the King. Upon hearing this, Liu An, believing these were immortals, was overjoyed and eagerly opened the door to welcome them.

However, upon seeing the eight old men, he couldn't help but burst into laughter. It turned out that all eight men had white hair and silver beards; although they looked hale and hearty, they were clearly old! How could they possibly possess techniques to prevent aging? 'You yourselves are so old, how can I believe you have methods to prevent aging? This is clearly a trick!' he exclaimed, ordering his guards to drive them away.

The eight old men exchanged glances and laughed heartily, 'Does the King of Huainan dislike our old age? Very well! Let him take a closer look at us then!' As they spoke, in the blink of an eye, all eight old men suddenly transformed into children.

It is utterly impossible for an old person to suddenly revert to childhood, so this is merely a legendary tale. The idiom '返老还童' (fǎn lǎo huán tóng) as mentioned in the Taoist scripture 'Yunji Qiqian' also refers only to legends related to alchemy and magic.