[Source] Han Fei (Warring States Period), "Han Feizi · Wai Chu Shuo Left Part One".
[Meaning] "Dú" refers to a wooden box; "huán" means to return; "zhū" refers to a pearl. To buy the ornamental case and return the pearl inside. This idiom metaphorically describes placing undue importance on superficial appearances while neglecting the intrinsic value, thus making an inappropriate choice by prioritizing the secondary over the essential.
[Historical Anecdote]
During the Spring and Autumn period, there was a gem merchant in the state of Chu. He conducted his business with great integrity, earning widespread trust, so many people preferred to buy jewels from him. One day, the merchant acquired a beautiful pearl. Intending to sell it, he decided to package it elaborately, believing that with a luxurious container, the pearl’s perceived value would naturally increase.
Thus, he procured precious wood and hired a highly skilled craftsman to make an exquisite box (i.e., "dú") for the pearl. He熏ed the box with fragrant spices such as cassia and pepper, filling it with a pleasant aroma. Then, he meticulously carved beautiful patterns on the exterior and inlaid it with elegant metal trim. The box sparkled beautifully and was truly a refined and exquisite work of art. The gem merchant carefully placed the pearl into the box and took it to the marketplace to sell.
Soon after arriving at the market, many people gathered to admire it. A man from the state of Zheng held the box, examining it for a long time, completely captivated. Eventually, he paid a high price to purchase the merchant’s box.
After paying, the man began walking home with the box, but had not gone far when he turned back. The merchant, thinking the man had regretted his purchase and wanted a refund, hadn’t finished his thought when the man approached him. The man opened the box, took out the pearl, and handed it to the merchant, saying, "Sir, you seem to have forgotten a pearl inside this box. I’ve come back on purpose to return it to you." With that, he handed over the pearl and then, head bowed, continued walking home while admiring the wooden box.
The gem merchant stood there, holding the returned pearl, utterly embarrassed. He had expected people to appreciate the pearl, but never imagined that the exquisite outer packaging would surpass the value of the pearl itself, overshadowing its true worth and leaving him utterly perplexed and helpless.