48 Why do the boys want to find “Number Two”?

"Number Two" is the place where Injun Joe hid the treasure.

“Now where’s your Number Two? ‘under the cross,’ hey? Right yonder’s where I saw Injun Joe poke up his candle, Huck!”
Huck stared at the mystic sign awhile, and then said with a shaky voice:
“Tom, less git out of here!”
“What! and leave the treasure?”