Minecraft wiki entry for Gathering_resources_on_peaceful_difficulty, associated text: One of the most important crafting products are sticky pistons. Three sticky pistons spawn naturally in jungle temples. However, jungle temples are very rare, so make sure that if you're looting a jungle temple in Peaceful difficulty, grab all 3 sticky pistons. You will find that they are very useful in redstone contraptions. Sticky pistons also generate in ancient city.