The Imperial Regalia of Japan, known in Japanese as the Sanshu no Jingi or Three Sacred Treasures, are the trio of objects that legitimise the reign of each Emperor of Japan. They consist of the sword Kusanagi-no-Tsurugi, the mirror Yata no Kagami, and the curved jewel Yasakani no Magatama. Among these three, only the magatama is a gemstone object in the strict sense, but all three are inseparable in the regalia tradition and together represent the oldest continuous body of dynastic insignia in the world.

The Yasakani no Magatama

The Yasakani no Magatama is a comma-shaped or foetus-shaped bead of the type known generically as a magatama, an archaeological form found across the Japanese archipelago and the Korean peninsula from the Jōmon period onward. The historical regalia bead is traditionally described as a large jewel, though no public examination has ever been conducted and the material is not officially confirmed. Comparable royal magatama recovered archaeologically are typically of nephrite jade from the Itoigawa region of Niigata Prefecture, with smaller examples in agate, jasper, serpentine and rock crystal. The shape, with a perforated bulbous head tapering to a curved tail, is so distinctive that magatama beads are an instantly recognisable signature of early Japanese material culture.

The Sword and the Mirror

Kusanagi-no-Tsurugi, the Grass-Cutter sword, is recorded in the Kojiki and Nihon Shoki as having been drawn from the tail of the eight-headed serpent Yamata no Orochi by the storm god Susano-o, then passed to the sun goddess Amaterasu and through her to the imperial line. Yata no Kagami, the Eight-Span Mirror, is associated in the same texts with the cave myth in which Amaterasu was lured from hiding by her own reflection. Both objects are housed at sanctuary shrines, the sword traditionally at Atsuta Jingu in Nagoya and the mirror at the Inner Shrine of Ise, with replicas held at the Imperial Palace in Tokyo.

Function and Inaccessibility

The regalia function as proof of legitimate accession. They are formally transferred at each Sokuirei accession ceremony, most recently in May 2019 when Emperor Naruhito acceded after the abdication of his father Akihito. At the Kenji-to-Shokei-no-gi rite, the sword and the magatama are presented to the new Emperor along with the State and Privy Seals, while the mirror remains at Ise. None of the three regalia is ever shown to the public. They are traditionally not seen even by the Emperor himself, being wrapped and enshrined; new emperors are ceremonially presented with covered boxes.

Material Speculation

Because no scholar has examined the regalia in modern times, gemmological discussion of the magatama is necessarily speculative. The most reasonable identifications, based on contemporaneous archaeological parallels from the Kofun period and earlier, would be Itoigawa nephrite, an Itoigawa-type jadeite where green colouration is described, or possibly a high-quality Japanese rock crystal. The size given in the chronicles is large, which is consistent with a chieftain-class or royal-class magatama of the kind recovered from imperial-period burial mounds. Replacement regalia have been recorded in the historical chronicles after losses at sea and fires, and what is venerated today may include components reconstituted at various points in the long medieval history of the line.

Cultural Standing

The regalia stand alongside the Stone of Scone, the Iron Crown of Lombardy and the Imperial Regalia of the Holy Roman Empire among the surviving dynastic insignia of the world's longest-recorded monarchies. For the Japanese gem trade, the magatama tradition is also a continuous design lineage. Magatama in jade and other materials are still made and worn, and the form recurs in contemporary Japanese fine jewellery and in the iconography of Shinto shrines.