I had the idea recently of using the facts that a diamond shape looks the same upside down, and that 6 and 9 look like each other upside down, as a two-way out for a prediction. I don't recall seeing this before, but I'm certain it must be in our literature somewhere. If anyone's seen it, could you please let me know where? Thanks!

Hello Jon,

I can't speak for the diamond, but with regard to 6 and 9, I took it one step further and used 86 and 98 as a two-way out in my routine exploiting Futagawa's force. This appeared in my Hidden Numerical Forces, (Orlando, Florida: Leaping Lizards Magic, 2006), pp. 138-144.

Thomas Henry

You are right, it is very likely that many people have invented this independently of each other.

I found the idea in the magazine of the Austrian magic societies "Aladin" (in German language). The bibliographic source is:

Werner Zuleger: Eine Voraussage (fast) ohne Vorbereitung, in: Aladin, vol. 23, no. 6, Nov/Dec 1971, p. 106