Hyperbole

Deliberate exaggeration, which no one takes literally, used to add emphasis to a feeling or a situation.

In Don Quixote

so, Sancho, for what I love Dulcinea del Toboso, she is worth as much as the highest princess on earth [...] I paint her in my imagination as I desire her, both in beauty and in preeminence.

Dulcinea "is worth as much as the highest princess on earth," and the measure of the exaggeration is the gentleman's love, which he himself says is enough to raise a farm girl to the highest post in the world.

Part One: The Penance and Micomicona, Don Quixote, to Sancho, after learning that the squire knows Aldonza Lorenzo

take this hand, lady, or, to put it better, this executioner of the world's evildoers; take this hand, I say, which no other woman's hand has ever touched, not even that of the one who holds full possession of my whole body.

Part One: The Arms and the Captive, Don Quixote, from atop Rocinante, to Maritornes, whom he takes for a lovesick maiden

did I not tell you a thousand times that in all the days of my life I have not seen the peerless Dulcinea, nor have I ever crossed the threshold of her palace, and that I am in love only from hearing tell of the great fame she has for beauty and discretion?

Part Two: The Printed Book, Don Quixote, to Sancho, in the streets of El Toboso, at midnight

Dulcinea del Toboso is the most beautiful woman in the world, and I the most unfortunate knight on earth, and it is not right that my weakness should defraud this truth. Tighten your grip on the lance, knight, and take my life, for you have taken my honor.

Part Two: The Defeat and Death, Don Quixote, knocked down on the beach at Barcelona, to the Knight of the White Moon