In the third stanza, the speaker admits that they’ve forgotten “the names of the nine muses” (Line 8). This is the first reference to Greek mythology in the poem; later, the speaker references the mythical river Lethe. There are nine muses, each with a different governance: epic poetry, dance, hymns, and so forth. This line contains two meanings: the speaker has forgotten the factual data of this story, but they’ve also lost touch with the inspiration these muses brought them. Being unable to call them by name means the speaker has lost the ability to summon their influence.