New Zealand's Hidden Past by Ross Wiseman
The picture on the front of the book is from one of the maps carved into stone -- as you can see, Australia, New Guinea and New Zealand, fairly accurate but with some interesting errors and exaggerations.
It's not particularly easy to find, as it was a small publication run. But it has a forward by Sir Edmund Hillary which alone makes it worthy of reading. The author is an unusual fellow, as becomes apparent in his book. But I think there is definitely something to be said for his theory. Those rock markings are not Maori, they are undoubtedly antient, and the civilization who made them were long gone before the Europeans showed up with Captain Cook.
Let me know if you have difficulty finding a copy, and I will keep an eye open. They sometimes come available.