Hmm, I'm still not sure what you mean. They definitely planned to have the effect that they have today, but something held it up (I think), and they came up with this thing as a temporary substitute. After all, you couldn't very well have people just looking at themselves in mirrors, and nothing more. Something had to be put in, and clouds of wispy ghosts surrounding the buggies was relatively easy to do, using a curved screen and projections of wraith-like spirits moving along horizontally, like the mist effects in the load area and in the graveyard. The blueprint plainly shows the projectors and the screen; what you don't know is what the projections were. What I remember is wispy clouds of ghosts, and the contemporary newspaper account of peering into a "fog" in the mirrors fits that pretty well, so I've got at least partial corroboration.