Cats do not do this naturally, I actually consider it pretty cruel to for a cat to do, and stressful for the cat. As a result if you give them litter they will likely use it instead, it is their instinct to do their business in the ground, with burying... not balancing on top of some water (their most hated enemy

). For old or unwell cats this is especially unkind to expect them to do as it becomes more difficult for them, and if they fall in they will likely not try again. They are also very likely to poop or pee on floors, in bathtubs, sinks, on tiles, bedding... everywhere, after being "toilet" trained. If you move the cat must be retrained with each toilet, they are not instinctively seeing every toilet as a place to go. Some cats will get so confused they'll just start going on the floor and not stop, even after giving them back a litter box... it's very hard, to even impossible, to reverse the behavior of going inappropriately once it starts. Actually, when you search online, most stories are horror stories, not successful ones.