The Imperial Regalia of Japan consists of a legendary sword, mirror, and jewel. They are brought out at every imperial enthronement, but only a few priests and the emperor himself are ever allowed to see them.
It is quite common for longstanding dynasties to claim a divine origin. Less common are dynasties that claim to have actual artefacts of divine origin to support that claim. And still less common are dynasties that still have the physical artefacts today.
The Imperial Regalia of Japan consists of three items:
- Kusanagi-no-Tsurugi, the grass-cutting sword
- Yata no Kagami, an octagonal mirror of wisdom
- Yasakani no Magatama, a large jade jewel
Shinto holds that these three treasures all come from the gods. The god Susanoo chopped the sword out of the body of an eight-headed serpent and gave it to his elder sister Amaterasu. The god of mirrors, Ishikori-dome no Mikoto, made the mirror and used it and the jewel to lure Amaterasu out of a cave (one of history’s many “a hero brings light to the world” myths).
By Shinto tradition, the three treasures came into the possession of Japan’s first (legendary) emperor, Jimmu about 2600 years ago. And they’ve been in the family ever since.
Well, perhaps. Various stories state that some or all of the imperial regalia have been lost. In 1040 CE the box containing the mirror burned up in a fire; only the guardian priests know the true extent of the damage. In the Battle of Dan-no-ura in 1185 CE the grandmother of the child emperor Antoku threw the sword and jewel (plus the child emperor himself!) into the sea rather than risk them being captured. The jewel was soon recovered, but the sword was either lost forever, or replaced with a replica made five hundred years earlier. The emperor, of course, drowned.
Today, Shinto priests guard the imperial regalia at three separate sites: Nagoya’s Atsuta Shrine, the Ise Grand Shrine, and the Imperial Palace itself. They only ever come out for imperial abdications and enthronement. When they do, they stay under wraps; we don’t have any idea what they look like or if they even still exist. Wikipedia has an artist’s impression of what they may look like, given our knowledge of Japanese design:
The Generalist Academy 
