That expression would most likely be a hyperbole. When you use hyperbole's you are most of the time exaggerating. So in this passage, the person is exaggerating when saying "seal me up and send me away". The person is acting as if he wants you to stuff him in the mail. For example" I laughed so hard I peed my pants". That is a hyperbole because you are exaggerating that you peed your pants. (Unless you actually did) :)
