A Cloning Machine! Just Choose what you want cloned, Hold it in you hand and jump in the water. Then hurry and click the crafting table and place the selected object in the middle. Wait until you hit the portal, Jump out there should be a clone to the first object, you probably cant pick it up, so open you inventory and take the original object and move it. Then the new item should appear. Right click it all over you inventory to gain infinite items! Enjoy!