Speaker, we hardly knew thee! We really don't get much info on the poetic speaker in "Proem." There's no "I" or "you"—the whole thing is very impersonal, really. However, the speaker sure knows a lot about poetry and wants to let it out!
The philosophical and historical references let us know that the speaker is an educated person, and while references to Plato or Epicurus might be found in almost any Western poem that wants to show off its classical knowledge, bringing up King Neza lets us know that this speaker has some relationship with Mexico.
Beyond that, though, this speaker is a person who delights in the possibilities of imagination. We mean, come on! Words that parachute onto the "sands of a page"?! That is wild, wacky stuff, gang. That this would even occur to the speaker indicates the power of his (or her) imagination, as well as the burning curiosity that drove him (again, or her) to this investigative thinking exercise in the first place!