We are looking for examples of exaggeration and overstatement when we look for hyperbole. One example can be found in Chapter XXXII when Huck discovers that the Phelps family believes that he is Tom Sawyer, arrived for a visit.
When Mrs. Phelps introduces Huck to Mr. Phelps as Tom Sawyer, Huck describes his reaction with hyperbole, saying:
"By jings, I most slumped through the floor!"
For obvious reasons, this is impossible and so must be taken as an overstatement for effect, i.e., hyperbole.
Earlier in the novel, at the end of the Grangerford episode, Huck runs for the raft and hopes to find Jim but cannot. He yells out and Jim responds. Huck describes hearing Jim's voice, stating that "nothing ever sounded so good before". This may be a literal truth but can just as easily be taken as an example of hyperbole as the statement presents a significant degree of extremity.
When a statement as absolute as this one is made, it is often an example of hyperbole.