Shirakumo to yoso ni mitsureba ashihiki no yama mo todoro ni otsuru takitsuse - Kinyo Wakashu(English Translation & Meaning)

白雲とよそに見つればあしひきの
山もとどろに落つる滝つ瀬

Roma-ji: Shirakumo to yoso ni mitsureba ashihiki no yama mo todoro ni otsuru takitsuse
English Translation: When I saw it far
I thought it was a white cloud,
but here, foot-wearying
mountains are made to thunder
by the torrent falling down
Meaning: Seen from afar, I took it for a white cloud, but here it is a cascade plunging down so mightily that the very mountain roars.
Commentary: Book Nine Miscellaneous Poems I 545

Seen from afar, the poet took it for a white cloud, but up close it was a cascade falling with such a roar that the very mountain resounded. The surprise of finding that a waterfall which looked like a quiet white cloud from a distance had, close at hand, power enough to shake the mountain is expressed through the contrast of far and near.
The next poem, 546, also sings of the Nunobiki Falls, so two poems on waterfalls stand together. Where this poem likens the falls to a white cloud, the next likens them to the lower course of the River of Heaven, both comparing the falls to something in the sky.
The author, Tsunenobu, is Minamoto no Tsunenobu. A son of the Minister of Popular Affairs Michikata, he rose to Major Counselor and was known as the Katsura Major Counselor. He was the father of Minamoto no Toshiyori, compiler of this anthology.

First line, 'shirakumo to', means as a white cloud, likening the falls seen from afar to a white cloud.
Second line, 'yoso ni mitsureba', means because I saw it from afar, the realis of the perfective tsu followed by ba.
Third line, 'ashihiki no', is a pillow word for mountain.
Fourth line, 'yama mo todoro ni', means so that even the mountain roars, todoro describing a great resounding noise. It sets the thunder of the falls heard up close against the distant view of yoso ni in the second line.
Final line, 'otsuru takitsuse', means the falling cascade, closing on a noun to impress the power of the falls.
Author: Minamoto no Tsunenobu
Source: Kinyo Wakashu
Prev Poem: Tamakushige Futami no ura no kai shigemi makie ni miyuru matsu no muradachi
Next Poem: Ama no gawa kore ya nagare no sue naramu sora yori otsuru Nunobiki no taki