I+could+scarcely+contain+my+feelings+of+triumph

"I could scarecly contain my feelings of triumph"

On http://www.thefreedictionary.com/triumph I found the defininition of the word triumph:
 * 1.** To be victorious or successful; win.**2.** To rejoice over a success or victory; exult

So in the sentence above, Poe was saying that the crazy man could hardly contain his feelings of being victorious.