Bushu Tamagawa (The Tama “Jewel” River in Musashi province)

The Jewel River in Musashi Province (Musashi Tatsukuri) is known as one of the Six Jewel Rivers (Mu Tamagawa) often depicted as a subject of allusive picture (mitate-e) of beauties by many artists.
This river is written in a poem by an unknown poet contained in vol. 14 of the Man'yoshu (Collection of a Myriad Leaves), the anthology of classic verse written before 760:
Tamagawa ni sarasu tetsukuri sarasarani mukashi no fude to sarani omowazu
(When I bleach the softest hand-made cotton in the Jewel River, I recall the love letter I once wrote to you.)