classic waka stream

鵲の渡せる橋に置く霜の
白きを見れば夜ぞ更けにける
Roma-ji

Kasasagi no wataseru hashi ni oku shimo no shiroki o mireba yo zo fukenikeru

English Translation
On the bridge that spans
the sky, laid by magpies' wings,
the frost has settled;
when I see how white it lies,
I know the night has grown late
Meaning
When I see how white the frost lies on the bridge the magpies spread across the sky, I know the night has grown late.
Commentary
Book Six Winter Poems 620

Headnote continued from the preceding poem: "Topic unknown."
This is the tenth poem of the frost-and-withering sequence. Seeing how white the frost lies on the bridge the magpies spread, the speaker knows that the night has grown late. The headnote continues from the preceding poem with no topic given, and the circumstances of composition are not recorded.
The author, "Middle Counselor Yakamochi," is Ōtomo no Yakamochi. A son of Ōtomo no Tabito, he rose to Middle Counselor. A poet thought to have been deeply involved in compiling the Man'yōshū, he is one of the Thirty-Six Poetic Immortals.
The scene is late on a winter night, and the place is where one can see the frost on "the bridge the magpies spread."
The direct occasion is not recorded.
This poem does not appear in the Man'yōshū; it was handed down in Yakamochi's personal collection and was also chosen for the Ogura Hyakunin Isshu.

The first line, "kasasagi no," refers to the magpie, a bird of the crow family. It rests on the Chinese legend that on the night of Tanabata magpies link their wings to bridge the River of Heaven for the Weaver Maiden to cross.
The second line, "wataseru hashi ni," means "on the bridge they have spread," with "ru" as the attributive form of the auxiliary of continuance "ri." It has been read both as the heavenly magpie bridge pictured in the winter night sky and as the palace stairs likened to that bridge.
The third line, "oku shimo no," means "of the frost settled on the bridge" and modifies "shiroki," whiteness, in the fourth line.
The fourth line, "shiroki o mireba," means "when I see its whiteness."
The last line, "yo zo fukenikeru," is a kakari-musubi construction in which "zo" is answered by "keru," the attributive form of the past auxiliary "keri." The poem knows the lateness of the night from the whiteness of the frost, and it shares with 611 in this book, which sang of frost on Uji Bridge, the scene of frost upon a bridge, so that the earthly Uji Bridge and the heavenly magpie bridge answer each other within the frost sequence.
Author
Otomo no Yakamochi
Source
Shin Kokin Wakashu
Other