Allusion in Sonnet 18

Allusion Examples in Sonnet 18:

Sonnet 18 1

"Shall I compare thee to a summer's day?..."   (Sonnet 18)

The beginning of this sonnet plays on the proverb “as good as one shall see in a summer’s day,” meaning “as good as the best there is.” The speaker is essentially asking, shall I compare you to the best of the best?