Historically, it is very far from the known truth, but I have picked up a hint for anyone trying to explain the facts of life to their daughter, if such a necessity still exists in this day and age.
The Lady is trying to help Anne of Cleves decide whether her marriage has in fact been consummated, as she doesn't seem to know. She explains:
"He has to insert his member into you and stir it".
So there you have it, plain and simple. I am still trying to picture the stirring; reminds me a little of a James Bond cocktail - shaken not stirred!