Yasakani no Magatama (comma-shaped jewel) (八尺瓊勾玉)

The Yasakani no magatama is one of the Three Sacred Treasures of the Imperial Family, along with the Yata no Kagami (the eight-span mirror) and the Ame no Murakumo no Tsurugi (the sword Ame-no-Murakumo, literally "Heavenly Sword of Assembled Clouds").
Usually written as '八尺瓊勾玉,' it is also written with the characters '八坂瓊曲玉.'

It has been handed down as a large magatama (a comma-shaped bead) or a magatama connected to a long strap.
The kanji character '尺' (shaku) is used to express the phonetic sound of 'saka' in 'Yasakani.'
The original meaning of 'saka,' however, means '咫' (ata) which stands for a unit of length used in ancient times. In this regard, with the character '八' meaning 'eight' and being used to represent the 'ya' of 'Yasakani,' the portion of the word read as 'Yasaka' appears to mean 'eight saka' or 'eight aka' (which would be about 1.4 meters), but the actual meaning is simply extraordinarily large or long. There is another theory that the origin of the term is 'iyasaka,' meaning happiness and prosperity.
The character used to represent the sound of 'ni' of Yasakani is '瓊' which means 'red orb.'
The jewel is sometimes referred to as 'ji' (a sacred jewel). When the jewel is combined with the sword, together they are referred to as 'Kenji,' meaning the Sacred Sword and the Sacred Jewel. There is a theory that the jewel symbolizes the moon (yin or negative) in contrast to the Yata no Kagami, which symbolizes the sun (yang or positive).

According to Japanese mythology, the jewel was made by Tamanooya when Iwato-gakure (the hiding of Amaterasu Omikami, the sun goddess, in the heavenly rock cave) happened, who was the deity from which Tamasuri no muraji descended. Along with the Yata no Kagami, the jewel was hung on a sakaki (species of evergreen sacred to Shinto), held reverently in both hands by the god Futodama. Later on, it is said that the jewel was given to Ninigi (the grandson of the Sun Goddess) during the 'Tensonkorin' where he descended to earth in order to rule the country.

At present, the Yasakani no magatama is said to be enshrined together with the sword in the Kenji no Ma (hall of sacred sword and jewel), situated beside the bedroom of the emperor in the Gosho (Imperial Palace).