Here is the last in a large collection of haiku written by Clark Ashton Smith (CAS). As with many of his other poems in the haiku form, "Tule-Mists" was unpublished in his lifetime. It's not available on The Eldritch Dark, so here's the complete text:
The fumes of cauldrons chill
Engulf the sanguine afternoon.
The common name "tule" usually refers to Schoenoplectus acutus, a marsh plant that is common in CAS' home state of California. The poem seems to describe the phenomenon of "tule fog", which the relevant Wikipedia article notes as "the leading cause of weather-related accidents in California."
The phrase "fumes of cauldrons chill" lends a sorcerous note to this short verse, which gains even more power after the enjambment where the word "Engulf" provides a sense of that dark power spreading across the landscape of a "sanguine afternoon."