Although this poem from Clark Ashton Smith (CAS) violates the accepted structure of the haiku in English (three unrhymed lines of five, seven, and five syllables), it substitutes a very effective structure of eight, six, and six syllables. This adds a momentum to the reading, which is solidified by end rhymes in the last two lines.
The elegant structure of this poem is greatly enhanced by the careful use of punctuation (two commas, a colon, and a period) to add explicit caesuras, so that when the text is read aloud, those pauses create a four-beat rhythm which comes so naturally to English speakers.
Despite the brevity of this work, it's obvious that CAS put some effort into it, as the structural elements noted above are quite thoughtfully developed. It would be fascinating to learn how much time CAS worked on this poem, and how much revision he did along the way. Alas, I suppose we'll never know!