Yosef Karo

“ However, if you pour from the crack, it is permitted since the vessel can hold a reviis under the crack.
3 A vessel that holds a reviis when it is propped up (by something else) and if it is not propped up will pour out the water so that not even a reviis of water remains in it is not a vessel. Therefore, the body of a (rounded) single piece barrel that doesn't hold a reviis when it is not supported should not be used to wash with. If it is wide enough on the bottom that it does hold a reviis while unsupported, you can wash with it. ”

“ There are those who say that a child under the age of six is considered like a monkey.
12 If the monkey [RAMA: This is a kind of beast that we call simia] pours water over one's hands some consider this invalid, while some consider it valid, which seems correct. ”