We aligned the pyramid so that the sides of its square base sat parallel to the four directions of the compass, and we let it sit there for about 24 hours, on a cupboard in his workshop behind the garage. The next day, my brother and I held the compass that we had used for calibrating the pyramid's orientation over the top of the pyramid — as had been described in some literature we had read about it — and the needle started spinning like crazy. I don't exactly remember anymore whether it was clockwise or counterclockwise, but I believe that it may have been clockwise.
We then called out to our dad to come over to the workshop and we repeated the experiment, with the same result, so he got to see it with his own eyes as well.
That's about as much as I remember, but I believe that my dad may have experimented some more with certain things he put inside the pyramid at either 1/3 or 2/3 of the height.