[masraum]

2 mirrors at a 90° angle in front of your face would do it.

The deal is this, most folks have a dominant eye, and I believe that it's possible for the brain to make either eye dominant. So you would see whatever the dominant eye is seeing.

When you look through a telescope when studying the stars or when you fire a gun, you're only using one eye, but it's generally considered best practice to keep both eyes open.

focus on something, now put one hand a few inches out from your face in front of one of your eyes. You can still see and maintain your focus on the item that you only see with one eye. Your brain will mostly block out the fact that the second eye is just seeing your hand.

The brain is an amazing thing.

Either that, or it'll be like crossing the streams which as we all know, is very bad.