I came across a rather good poem by Michael Field (actually a pseudonym for an incestuous aunt-and-niece literary double act) the other day, which begins 'Adown the Lesbian vales'. It's just a bit too long to post in full here, but here's a link.

The poem begins with a quotation from Sappho, and is full to the gunwales with references to Greek mythology. I think I can decode all of these, apart from the last line of the last verse. This is that last verse:

To that pure band alone
I sing of marriage-loves;
As Aphrodite's doves
Glance in the sun their colour comes and goes:
No girls let fall
Their maiden zone
At Hymen's call
Serene as those
Taught by a poet why sweet Hesper glows.

I have at least a rudimentary knowledge of classical literature, but I am not aware of any famous classical poem giving an explanation for the luminosity of the evening star. Is there such a poem? Or is 'a poet' a reference to the authors of this poem?