That '70s Episode - S1-E17

Question: When Grams talks with Patty on the phone, Phoebe was surprised that their mom said she had a premonition, and then mentioned that Prue told her that Patty had the power of freezing. How did she or any of the girls know what kind of power Patty could have?

Chosen answer: Most likely from the Book of Shadows, since it's not only a spell book, but a history of the Hallewell line.