What aesthetic message does Edmund Spenser convey in "One Day I Wrote Her Name"?
I understand aesthetic in this context to mean the Kantian objective and universally recognized beauty that combines aesthetic and taste for evaluations that call on the intellectual, the sensory and the emotional simultaneously. In this case, the aesthetic message Spenser conveys in "One Day I Wrote Her Name" is embodied in "but you shall live by fame; / My verse your virtues rare shall eternise, / And in the heavens write your glorious name...."
Spenser is giving the aesthetic message of the immortality of art, specifically, the immortality of poetic words. Spenser along with Phillip Sydney (Spenser's nephew) adhered to the poetic mimetic theory, which is briefly that inspired poets attuned their words to the inspiration of God and therefore human souls were drawn to recognize it as beauty and truth. In thus being drawn, they would desire to emulate the goodness revealed therein. The immortality in the aesthetic of Spenser encompasses much more than that people hundreds of years later would read his words and embrace the lady at the "stand" (beach); it encompasses poetry's Divine inspiration and inspired force to compel human imitation of the divine. In the case of Spenser and his lady at the strand, the mimesis would be of divine love.