At the round earth's imagined corners (Holy Sonnet 7)
Analysis: Calling Card
Poor Petrarch. The guy practically invented the sonnet form, and the first great sonnets were in Italian. Nowadays, school kids hear sonnet and think "Shakespeare, Shakespeare, Shakespeare."
Fortunately, Donne kept the flame going for the Italian sonnet form and its division into an eight-line octet and six-line sestet. There are plenty of other English poets who have used the Italian form, from Thomas Wyatt to John Milton. But Donne gets extra points because he wrote Petrarchan sonnets immediately in the wake of Shakespeare, who reinvented the sonnet form.