Bronze Mirror Excavated from Mitarai Pond on Mount Haguro

Bronze Mirrors Excavated from Mitarashi Pond at Mt. Haguro: A Window into Heian-Period Faith and Artistry

Held at the Hosomi Museum in Kyoto, the collection of forty bronze mirrors known as the "Haguro-kyō" stands among the most evocative cultural treasures of Japan's Heian period. Each mirror was once cast into a sacred pond on the summit of Mt. Haguro in present-day Yamagata Prefecture, offered to the deity believed to dwell within its waters. When the pond was drained for restoration work in the early twentieth century, these mirrors returned to the light after nearly a thousand years beneath the surface—silent witnesses to a uniquely Japanese form of devotion. The Hosomi Museum, in the quiet Okazaki cultural district of Kyoto, now offers visitors from around the world a rare opportunity to encounter these radiant objects of faith and refinement.

The Sacred Pond and the Faith of Pond Mirror Offerings

Mt. Haguro is one of the three peaks of the Dewa Sanzan in Yamagata Prefecture—an ancient center of mountain worship and Shugendō ascetic practice that has drawn pilgrims for more than a millennium. At its summit, just before the Sanjin Gōsaiden (the joint hall enshrining the deities of Mt. Haguro, Mt. Gassan, and Mt. Yudono), lies an oval pond about 38 meters across known as the Mitarashi Pond, or more familiarly as the Kagami-ike ("Mirror Pond").

The pond was not simply a place of ritual purification. In ancient writings, the very characters for "Haguro Shrine" were read as ikenomitama, meaning "the spirit of the pond"—a vivid reminder that the water itself was believed to be the body of the deity. The deity was identified with Kuzuryū-ō, the Nine-Headed Dragon King, ruler of waters and bringer of rain. From the late Heian period onward, devout worshippers would consign precious bronze mirrors to the pond as votive offerings, a practice known as ikechū nōkyō—"depositing mirrors within a pond." It was an act of profound reverence: relinquishing one of the most personal and treasured possessions of the age to the unseen power dwelling in the depths.

When the pond was restored on four occasions between the early Taishō era (around 1912) and the early Shōwa era (around 1930), roughly five to six hundred mirrors were retrieved from its bed. They span the late Heian to the Edo period, but the bulk—and the most artistically distinguished—date from the twelfth century. The Mt. Haguro pond remains the single most prolific site of pond mirror offerings discovered anywhere in Japan, and the mirrors themselves have come to be known collectively as Haguro-kyō, "the Haguro mirrors."

The Hosomi Collection: Forty Mirrors of Heian Elegance

Following their recovery from the pond, the Haguro mirrors were dispersed among several institutions, including the Dewa Sanzan History Museum at Mt. Haguro itself, the Tokyo National Museum, and the Hosomi Museum in Kyoto. The forty mirrors held by the Hosomi Museum Foundation have been collectively designated an Important Cultural Property by the Japanese government, recognizing both their religious significance and the exceptional quality of their craftsmanship.

The Hosomi Collection was assembled over three generations by the Hosomi family, beginning with Hosomi Ryōichi (1901–1978), an Osaka-based industrialist who began his collecting life with metalwork before broadening his focus to Buddhist painting, Rinpa screens, and works by Itō Jakuchū. Bronze mirrors and other metal arts remained a particular strength of the collection, and the forty Haguro mirrors are among its most cherished holdings.

What distinguishes this group is its concentration on the wakyō—Japanese-style mirrors—of the late Heian period. By the twelfth century, Japanese mirror-makers had moved away from the heavy Tang-Chinese prototypes that had earlier been imported through the continent, and had developed a distinctive native style: thinner in profile, lighter in hand, and with backs decorated not in continental motifs but in scenes drawn from the seasonal landscapes of Japan. Pairs of birds in flight among autumn grasses, willows and pines, plum blossoms and cherry, butterflies and dragonflies—the entire pictorial vocabulary of contemporaneous yamato-e painting—were rendered in low relief on the bronze, transforming an everyday object into an exquisite miniature canvas.

Why These Mirrors Were Designated an Important Cultural Property

The designation rests on several intersecting grounds. First, the Haguro mirrors represent the foremost concentration of pond-offering mirrors known in Japan, making them an irreplaceable archaeological record of medieval water-spirit worship. Second, the late Heian wakyō within the Hosomi group are among the finest surviving examples of their type, embodying the courtly aesthetic ideal often described as ōchō-bi, or "the beauty of the imperial court." Third, the mirrors are believed to have been produced in workshops in or near the capital at Kyoto and then carried to a distant mountain shrine in the far north, providing material evidence of the long-distance religious networks that linked the Heian capital to the sacred peaks of the Tōhoku region.

Taken together, the forty mirrors are at once works of art, devotional objects, and historical documents—a rare combination that fully merits their status as one of Japan's officially recognized cultural treasures.

Highlights to Look For

Visitors who encounter the Hosomi Haguro mirrors may wish to slow down and look closely at several features that reward careful observation.

The first is the variety of compositions on the mirror backs. Some show paired birds wheeling among grasses; others feature solitary cranes on pine branches, plum sprigs in bloom, or chrysanthemums tossed by an imagined wind. Each composition is asymmetrical and lyrical, much like a fragment cut from a hand scroll.

The second is the extraordinary thinness of the bronze itself. By the twelfth century, casting techniques had advanced to such a degree that mirrors could be made remarkably slender while still polishing to a brilliant reflective surface on the front. To hold one in the hand (as conservators occasionally do) is to feel how the mirror trembles like a sheet of paper.

The third is the patina. Centuries beneath the still waters of the Mitarashi Pond have produced a soft greenish-brown bloom on the bronze. Rather than diminishing the mirrors, this patina lends each one a quiet, archaeological presence that an undisturbed mirror could never possess.

Finally, look for the occasional appearance of imitation mirrors known as gikyō—rougher castings made to resemble true mirrors and offered, presumably, by worshippers of more modest means. They speak to the depth of the devotional impulse that brought offerings from every level of society to this remote mountaintop shrine.

Visiting the Hosomi Museum

The Hosomi Museum, which has stewarded the forty Haguro mirrors since the collection passed into the care of the Hosomi Museum Foundation, opened in 1998 in the Okazaki district of Kyoto's Sakyō Ward. Designed by the architect Ōe Tadasu, the museum building combines the warmth of traditional Kyoto townhouse motifs with a contemporary structure built around a vertiginous open atrium spanning the basement levels up to the third floor.

The museum does not maintain a permanent display; instead it presents rotating thematic exhibitions drawn from its rich holdings. The Haguro mirrors are exhibited periodically as part of these special exhibitions, often grouped with the museum's outstanding collection of Buddhist sculpture, Rinpa paintings, and Itō Jakuchū works. Visitors are strongly encouraged to check the museum's exhibition schedule before traveling, as the specific objects on view change with each show.

The museum also houses the Café Cube on its basement level and a tea room called Kokōan on the third floor, where visitors may enjoy a bowl of matcha and Japanese sweets. A small museum shop offers carefully curated publications and original goods.

Surrounding Attractions in Okazaki

The Hosomi Museum stands at the heart of one of Kyoto's most concentrated cultural districts. Within a few minutes' walk, visitors can also explore the Kyoto City KYOCERA Museum of Art, the National Museum of Modern Art Kyoto, and the Heian Jingū shrine with its grand vermilion torii gate. The path between these institutions runs through tree-lined avenues and the broad open space of Okazaki Park, which becomes especially lovely during the cherry blossom season in early April.

For those who wish to engage more deeply with the world that produced these mirrors, a visit to the Dewa Sanzan in Yamagata Prefecture offers a complementary perspective. The Mitarashi Pond itself can still be seen at the summit of Mt. Haguro, in front of the Sanjin Gōsaiden, and the nearby Dewa Sanzan History Museum exhibits another portion of the original mirror find. The mountain is reached most easily by bus from Tsuruoka, on the Sea of Japan coast.