Once upon a time, more than 1,000 years ago, there was a small island nation ruled over by an emperor and empress. Fascinated by what lay across the sea, the emperor sent out envoys to bring back treasures from afar — glittering glassware, lutes capable of talking with the gods, stunning ceramics and much, much more.

All was well until one day the aging emperor became sick and died. Grief-stricken and surrounded by her husband’s treasures, each of which triggered memories of their happy times together, the empress made a decision. She would pack up the mementos and send them all away to a temple, where her beloved would be commemorated for millennia.

A nice bedtime story? Perhaps, but it’s also historical fact. And the treasures — collected by Emperor Shomu and then dedicated en masse to the Todaiji Temple in Nara by his wife, Empress Komyo, in 756 C.E. — exist to this day. From Oct. 29 through Nov. 14, some 62 of them will go on display at Nara National Museum. And if past experience is anything to go by, for those 17 days the exhibition of the Shosoin treasures, as they are known, will attract an average of 15,000 people per day, making it by far the most popular exhibition in Japan and, arguably, the world.

Empress Komyo’s donation to Todaiji — which is famous for its giant statue of Buddha, which was in fact commissioned by her husband — consisted of more than 600 pieces from as far away as China, India, Persia and possibly beyond, and those were soon added to from other collections. In order to house what became a trove of 9,000 items, a wooden storeroom some 300 sq. meters in area was built on Todaiji grounds sometime before 759. And there the treasures stayed for over a millennium — somehow remaining almost unscathed by the ravages of war, tempests, earthquakes and the simple passage of time.

“We were told in school that the secret of the collection’s posterity lay in the design of the storeroom itself,” Kenichi Yuyama, the director of Nara National Museum, tells The Japan Times. “We were told that the wooden logs that make up its external walls contracted in the winter, thus providing ventilation during the dry months and expanded in the summer, thus keeping the storeroom protected from humidity in the hot months. But the fact is that it is airtight all year round.”

These days though, Yuyama continues, it is generally accepted that the key to the treasures’ longevity lies in the status of their owner.

“For most of that time, they were under the direct control of the Imperial family. That meant, to take them out of the storeroom, you had to actually obtain the seal of the current Emperor,” he says.

The Emperor wasn’t easy with his seal. The first time a significant number of the objects was displayed in Tokyo, Yuyama points out, was in 1940, when an exhibition of some 140 pieces was created to celebrate the 2,600th anniversary of the founding of the Empire.

“My aunt said she saw them then as a student,” Yuyama says. “Apparently more than 400,000 people went to the exhibition.”

But it wasn’t long before the collection was on the move again — albeit a much shorter journey. Toward the end of World War II, as fears grew that the wooden storeroom might be bombed by the Allies, it was decided to move its contents to the nearby Nara National Museum, which had a state-of-the-art concrete storeroom.

After the war, the public asked for the collection to be put on display before it was returned to the storeroom — and thus the first large-scale Shosoin exhibition was held, in 1946.

“Japan had lost the war, lost its confidence and was, as a nation, utterly dejected. The show reminded the people what a wonderful culture the country had,” Yuyama says, adding that some 150,000 people attended.

The collection was ultimately moved back to the wooden storeroom at Todaiji — and then to a new, dedicated concrete facility. Since then, for about three weeks every autumn, when the storeroom is traditionally opened for maintenance and conservation, a selection of roughly 60 items has been put on display at the Nara National Museum. This year’s is the 63rd such show.

Yuyama says it is the Office of the Shosoin Treasure House, within the Imperial Household Agency, that chooses which treasures will be displayed. “Each time, a handful of the most famous treasures are included — but they rotate them so any one will only be shown once every decade or so, and each year they also include 10 or so pieces that have never been displayed before,” he explains.

One of this year’s highlights is the kingindenso no karatachi, which translates as a “Chinese-style sword with gilded silver fittings and inlay.” The 99-cm ceremonial weapon, the sheath of which is in lacquerware decorated with colored glass and crystal, was kept in the North Room of the storeroom, meaning that it was one of the original pieces dedicated by Empress Komyo.

This will be the first time the sword, which was owned and perhaps even held by Emperor Shomu himself more than 12 centuries ago, will have been included in the Shosoin show since 1990.

Another highlight, Yuyama explains, will be a large piece of aromatic wood known as Ojukuko, from the Middle Room — meaning it came under the control of the Imperial family in the mid-Heian Period (794-1185). Measuring 1.5 meters in length, the wood is thought to be agarwood, a dark resinous heartwood that results when certain Southeast Asian trees become infected with mold.

So valued was the scent of this particular log that there are records of pieces being cut off by successive Ashikaga Shoguns during the Muromachi Period (14th-16th centuries), as well as by 16th-century warlord Oda Nobunaga and the Emperor Meiji during his reign from 1868 to 1912.

Like all the exhibits at the show, the wood will be exhibited within an airtight case, so visitors unfortunately won’t be able to smell it. But, as Yuyama told a Tokyo audience recently, “One envies the curator who will open the box after the show is finished.”

Other highlights will be three wooden masks that were used in gigaku, a form of dance drama that was imported from China in the 7th century and practiced at the Imperial court and in temples throughout the Nara Period (710 — 784). The masks, two of which have never been exhibited before, are considered some of the oldest masks of any kind in existence in the world.

There will also be many paper documents, including an 8th-century map of the Todaiji Temple complex. The map includes a drawing of the hall that houses the giant Buddha — looking surprisingly similar to how it looks now, despite being rebuilt at least twice.

Many items of fabric are included in the Shosoin collection, too, and this year a tie-dyed jacket decorated with bold diagonal blue stripes that was worn by court officials in the Nara Period will be displayed.

Yuyama explains that the Office of the Shosoin Treasure House is constantly conducting research projects into the various items in its collection. Himself a specialist in paper objects, Yuyama took part in a four-year research project that concluded last year. “We discovered for the first time that the plant kujin (Sophora flavescens), which is a well-known Chinese traditional medicinal plant, had been used in Nara Period paper manufacture,” he says.

Such research often focuses on attempts to determine just how the objects in the collection were made — and that research, in turn, often involves recreating the objects as realistically as possible. This year, results of research into the karatachi sword were published.

Lacquerware artist and living national treasure Kazumi Murose led the research, recreating the sheath to determine, in particular, whether the variously sized gold specks visible on its lacquered surface were alluvial gold or gold filings. In the most recent Bulletin of the Office of the Shosoin Treasure House, published earlier this year, he reported that it was “clearly” the latter.

Murose’s task was made easier by the fact that the Shosoin collection also includes a metal file that itself dates back to the Nara Period. Hence it was by making a file similar to the ones used when the sword was made that he was able to identify the gold specks as filings.

The variety and sheer number of objects in the Shosoin collection is one of the key reasons for its value.

“There are so many different types of things — from crafts, to paper items, dyed fabrics — there is no other collection that has such concentrations of these objects,” Yuyama says.

“As a researcher, it is an absolutely essential resource for understanding Asian history. You could never get tired of looking at it.”

The only problem is that having objects from such a rare collection displayed for just three weeks each year can result in huge crowds.

Every year, the Shosoin show tops rankings of average visitor numbers for exhibitions held in Japan, and if it was included in the U.K.-based Art Newspaper’s rankings for shows held around the world it would easily top them, too.

Yuyama suggests Oct. 31 — the first Monday after opening — as the day least likely to be crowded. Miss that and this stunning collection might have to remain the stuff of bedtime stories, at least for another year.

“The 63rd Annual Exhibition of Shosoin Treasures” will be open daily at Nara National Museum from Oct. 29 through Nov.14. General admission is ¥1,000. For further information, see www.narahaku.go.jp.