Ever since I picked up a book on toilet-training cats years ago I've been intrigued by the idea. The author claimed that it was possible to toilet train a cat by incrementally moving the litter box close to the toilet, raising it up, placing it on, then in, the toilet and once the kitty is used to this spot for doing his/her business, finally removing it. He made it sound quite reasonable and the thought of not having to scoop "treasures" out of the litter pan is appealing. The girls are smart enough and willing to learn new things so I figured we have nothing to lose (except the use of the downstairs bathroom while the training is going on!)
Over the course of 2 weeks we moved the box next to the toilet, raised it up on books gradually so that it was at the same height, and then placed it on top. So far, so good. Granted, we do have 2 other litter boxes in the basement which we'll keep there for Gomer and so the girls don't decide to leave 'surprises' around the house if the training doesn't go well, but there is plenty of evidence that the box on the toilet is being used regularly.
Today I replaced the litter pan with a small tray that fit perfectly down into the toilet bowl; this is a big step as it is much smaller than the girls are used to. Hopefully they'll be in the habit and will continue to use it. If not, I'll need to go back to the bigger box set on the toilet for a few more days and try again with the tray next week. With any luck, in another week or two they'll be making deposits into the toilet without any litter there. Best of all, we'll have the use of our downstairs bathroom again.