Luong The Vinh, the Measuring Laureate

A pomelo had just rolled straight down into a deep hole by the side of the road. Young buffalo herders stood around the rim, at a loss. The hole was narrow, and an arm reaching down could not touch the bottom. Poked with a long stick, the pomelo kept rolling away. The more they poked, the deeper it slipped into the dark corner.

They were pulling long faces over the lost fruit when one boy waved a hand and told his friends to wait. He ran off to fetch water, then poured it slowly into the hole. As the water rose, the light pomelo floated up with it. In a moment it was bobbing just below the rim, close enough to pick up by hand. The whole group clapped and cheered. The boy only smiled and brushed off his hands, as if it were nothing at all.

The old tellers say that the boy who thought of this way to save the pomelo was named Lương Thế Vinh. The pomelo story is only an anecdote. But that name is no made-up tale. It belongs to a real man in the history books. He came from the village of Cao Hương, in the district of Thiên Bản. Today that area lies in Ninh Binh province. At the age of 23, he went to the capital to sit the examination, and he passed at once as Trạng nguyên. Trạng nguyên was the title of the top graduate of the royal examinations. That was the examination of the year Quý Mùi, that is, 1463, in the reign of Emperor Lê Thánh Tông. More than 4,000 candidates came to sit it. Only 44 of them passed as doctoral laureates. Among those few, the best minds in the land, Lương Thế Vinh came first.

His greatest gift was for mathematics. He so loved calculating and measuring that, tradition says, he wrote a whole book to teach mathematics. It is called Đại thành toán pháp. It is considered the first mathematics textbook in the country. It taught people how to reckon the area of their fields, how to measure out rice, and how to divide shares fairly. Because he was better at mathematics and measuring than anyone, ordinary people stopped calling him Trạng nguyên. They gave him a fond name instead, and it stuck. They called him Trạng Lường. Lường means to measure.

People long ago told a great many merry anecdotes about this laureate who was so good at measuring. They are folk tales passed down by word of mouth, not history. But every one of them sparkles with a mind that knows how to think.

The best-loved of them is the tale of weighing the elephant. The old tellers say that an envoy once arrived from the land to the north. He had heard that the top scholar of the southern land was good at calculating, and he wanted to put him to the test. Standing on a riverbank, the envoy pointed at a huge elephant that was being led past. Then he challenged Lương Thế Vinh to weigh it.

An elephant is as big as a small hill, and there was no scale large enough to stand it on. The envoy felt sure that this time the laureate would be stumped. Yet Lương Thế Vinh only smiled. He had his soldiers lead the elephant down onto a large boat moored by the bank.

As soon as the elephant stepped aboard, the boat sank deeper into the water. The laureate had someone bring paint and carefully mark the waterline along the side of the boat. When that was done, he had the elephant led back onto the shore. Lighter now, the boat rose up again as before.

Then he ordered the soldiers to carry stones down into the boat. As more and more stones went in, the boat slowly sank again. He stood watching until the water reached exactly the paint mark, and then he told them to stop. The stones in the boat now weighed exactly as much as the elephant, he said. All they had to do was carry the stones up one load at a time and weigh each load. Added together, the loads would give the weight of the elephant, without the slightest error. The envoy nodded, wide-eyed, unable to find a word of criticism.

But the envoy was not finished yet. From his sleeve he drew a thick book and turned up one paper-thin page. Could Lương Thế Vinh measure the thickness of that single sheet, he asked.

This time the puzzle was truly hard. The sheet was so thin that it could hardly be felt between two fingers, and no ruler could take its measure. Even adults would have shaken their heads at it. Yet the laureate still had a way.

Lương Thế Vinh did not measure one sheet. He asked to borrow the whole book. With a ruler, he measured the thickness of the entire stack of paper, from the front cover to the back. Next he counted how many sheets the book held. Then he divided the thickness of the whole stack evenly by the number of sheets. The thickness of the whole book, shared out among all its sheets, gave the thickness of one. The figure that came out matched exactly the answer the envoy had been keeping to himself. At this, the envoy from the north was won over and genuinely impressed. He cheerfully admitted defeat and praised the southern land for truly having people of talent.

Both times, Lương Thế Vinh worked no magic. He did something simple that few would think of. When a thing is too big, too heavy or too thin to measure directly, find a roundabout way to measure it. He turned the elephant into a boatload of stones, which was easy to weigh. He turned a single sheet into a whole book, which was easy to measure. It was just as in his boyhood. Instead of fishing for the pomelo in the deep hole, he poured in water so that it floated up by itself.

More than 500 years have passed since that examination. In many provinces and cities across the country, there are still schools named after Lương Thế Vinh, ringing every day with the voices of children at their lessons. Sometimes a child stands puzzled before a riddle that seems to have no answer, then suddenly cries out, having found a clever roundabout way through. At such moments, it is as if the laureate of Cao Hương village, the one so good at measuring, is smiling somewhere, very close by.