Not a saying, but talk of toilet training brought back another memory of the same daughter the previous year (then 2 years old).
We were living in a bungalow in S. Africa, and it was summer, so I let her wander around with no panties. She wouldn't use a potty, and eventually insisted, after helping the drought by sprinkling the garden, that if she went anywhere she'd use the loo. Can't fault her on that: she used to potter off on her own, and climb on to face the cistern. One afternoon, she wandered back into the lounge walking with her legs wide apart and a pained expression on her face. I asked her why she was walking that way and she said her bottom hurt. I asked what had she done to make it hurt, and she said it was the talcum powder. There was no talcum powder close to hand. I asked where she had got it and she told me from the shelf over the bath. The only thing up there was the nappy cleanser powder, and she had had to climb up onto the side of the bath and stand on that to reach the tub!
A sit in a cool bath sorted her out. She's now training for the dignified profession of pharmacist. Obviously showied an interest in the reaction of chemicals on the human body at an early age!
Andrea