And speaking of Ernst Mach...
Here's an update on being able to see the photo below as it truly is.
With practice I've been able to veer in and out of the reality and the illusion of the photo and by looking at the top speaker and changing it's position by concentrating on the left line and telling myself that the speaker is sitting on top, pointing upward...does that make sense?
The Analysis of Sensations, Ernst Mach: "No point of view has absolute, permanent validity*. Each has importance only for some given end..."
I've been trying to tell people this* since I was 8 years old!!!