Cauldron

A Cauldron is a block that can be filled with water when right-clicked upon with a Water Bucket. When filled, a Cauldron can be used three times to fill three Glass Bottles, or, since 1.4, can be used to wash off the dye from Leather Armor. However, this consumes just as much water as using a water bottle. The Water Bottles, on the other hand, are key ingredients for the Brewing of Potions using a Brewing Stand. A Cauldron is currently—without the use of mods or cheats—the only way to get water into the Nether. Cauldrons can be found in Witch Huts, alongside a crafting table.

Trivia

 * Cauldrons cannot hold Lava or Milk, but the potions that were once put inside of it in Beta 1.9 Pre-Release 2 used the Lava texture.
 * When broken, Cauldrons that have water in it do not drop any water, only the Cauldron itself.
 * While a Cauldron that contains water is being broken, the water will show cracks as if it were a block.
 * Cauldrons can be used to legitimately store water within the Nether, as opposed to water evaporating by trying to place it down with a bucket or evaporating when created by melting ice. The cheat code  still works for getting water into the nether, but using cheat codes is not considered "legitimate".
 * Even if a Cauldron has water in it, a Piston can push it.
 * In creative mode, if you attempt to fly inside a cauldron with a block above your head, a glitch will occur causing you to be "stuck" in flight form without being able to lift or lower yourself.
 * Standing in a Cauldron while the cauldron is being pulled by a piston will cause you to go through the cauldron rather than to be carried with it.
 * On November 8, 2011, Jeb tweeted a reply to a suggestion for boiling food in a cauldron, saying he may consider it later.
 * It's possible to push a minecart inside of a cauldron by using pistons and slabs.
 * It is actually extremely inefficient to use cauldrons as a source to get water for potions since 1 source block of water is enough to produce an infinite number of water bottles, crafting a cauldron requires 4 more iron ingots than it takes to craft a bucket and a filled cauldron will only fill 3 bottles before it needs to be refilled itself. Thus, the cauldron's only actual purpose is for making potions in the Nether, or cleaning dye off leather armor. They are of some use, however, if used in zones far away from water sources to collect rainwater (For example, in a Superflat world).
 * Fire on anything but Netherrack goes out shortly after putting a Cauldron over it.
 * You cannot sneak across a cauldron, as you can still fall in.
 * Arrows "stick" to the water in a cauldron.
 * A cauldron has approximately a 15.5% chance of being filled with at least one level of water when exposed to one session of rainfall (Tested with 1000 cauldrons during a regular 15 minute rainfall session).
 * When standing in a cauldron with water on top the breath bubbles won't show up, but the player will drown.
 * Cauldrons will spawn in witch huts, however they are always empty.
 * The top of the hopper shares the same texture as the top of the cauldron.
 * The water in a cauldron will not damage Endermen.
 * Inside a Cauldron is 0.313 blocks tall.
 * If an entity is extinguished by a filled cauldron, the cauldron water lowers one water level.
 * You cannot throw a dropped item into the water in a cauldron. It will repeatedly bounce on the surface until it bounces clear or is grabbed by a player.