Good Hobbit Morning chapter 9 "Barrels out of bond"

"Thorin and the Dwarves are imprisoned on the orders of the Elvenking (Thranduil, father of Legolas), with Thorin in the deepest, darkest dungeon... Bilbo, still invisible, spots his opportunity: he steals the keys and sets the Dwarves free.

Bilbo stuffs them into the empty wine barrels, padding them with straw and drilling air holes in the barrels. The elves float the barrels down the river; the plan came close to ruin when the elves almost open the barrels due to their weight, however, the dwarves successfully escape to Lake-town."