classic waka stream

たぶてにも投げ越しつべき天の川
隔てればかもあまたすべなき
Roma-ji

Tabute ni mo nagekoshitsubeki amanogawa hedatereba kamo amata subenaki

English Translation
Even a pebble
one could surely toss across,
the River of Heaven:
is it that it lies between us
that I am so helpless?
Meaning
The River of Heaven is so narrow one could toss a pebble across it; is it because it still divides us that I am so utterly helpless?
Commentary
Book Eight Autumn Miscellaneous Poems 1522

Headnote continued from the preceding poem: "Twelve poems on the Tanabata festival by Yamanoue no Omi Okura"
The River of Heaven is so narrow that one could toss a pebble across it, yet because it separates the lovers, the speaker is utterly helpless. The contrast between the nearness and the uncrossable gap expresses the sorrow of being unable to meet. Like the preceding poem, the note dates it to the night of the seventh day of the seventh month of Tenpyō 1 (729).
The author, Yamanoue no Okura, was an official and poet of the early Nara period. He went to Tang China as a member of an embassy and later became governor of Chikuzen. He is known for poems that look closely at human life and society.

The first line means "even a pebble."
The second line, with the perfective "tsu" and potential "beshi," means "that one could toss across," showing how narrow the river is.
The third line names the river that divides the pair.
The fourth line, containing the particle "ka," surmises "is it because it divides us?"
The final line answers the "ka" of the fourth line with the attributive form, expressing helpless pain. The gap of a river both near and far is a theme running through the Tanabata sequence.
Author
Yamanoue no Okura
Source
Manyoshu
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