Minecraft wiki entry for Development_versions, associated text: More things will burn in the furnace
1 Wool smelts 0.5 items
1 Carpet smelts 0.33 items, just less than 1⁄3 items (increased in 16w35a)
1 Ladder smelts 1.165 items, just less than 1 1⁄6 items (increased in 16w35a)
1 Wooden Button smelts 0.5 items
1 Bow smelts 1.5 items
1 Fishing rod smelts 1.5 items
1 Sign smelts 1 item
1 Bowl smelts 0.5 items
1 Wooden door smelts 1 item
1 Boat smelts 2 items