Facts in Kubla Khan

Samuel Purchas’s Purchas, His Pilgrimes includes, along with descriptions of Xanadu, an account of Mount Abora in Ethiopia, once the ancient kingdom of Abyssinia. According to Purchas, Mount Abora was a place of overwhelming natural beauty—another Xanadu, one might say. The Abyssinian tradition held that all the king’s sons save for the heir would be sent to the royal prison atop Mount Abora to live out their days. The king feared the prospect of revolt by the non-heirs. This notion of infighting in Paradise brings to mind again the conflict between Kubla and Ariq.

The “ancestral voices prophesying war” is likely a reference to Ariq Böke, a Mongol general who was Kublai Khan’s brother and enemy in war. The intended feeling in these lines is that of trouble brewing outside of paradise. It is a reminder of the real world.

One of the steps in harvesting grain is known as “threshing,” which is a process of separating pure grain from the husk, or “chaff,” using a flail. This process is the origin of the idiom “separating the wheat from the chaff,” which refers to any process of discerning valuable things from worthless things. The thunderous river of the poetic imagination produces “chaffy grain”: plenty of waste along with the occasional gem. The imperfection of the artistic process is one of the poem’s central themes.

The gushing waters of the river erupted right behind the "huge fragments" of rock and earth that "vaulted" upward from the underground source.