Zemouregal's memory is a memory found during the Mahjarrat Memories miniquest. It can be found at the very end of Zemouregal's Base in the wilderness, in the map room. Note that you do not need to actually enter the Wilderness to get there, you can instead follow Hartwin in Varrock Palace. You need insulated boots and a Macaw familiar to reach it. When brought to Kharshai, he transcribes it into a book.