The Schulte Table was developed by German psychiatrist and psychotherapist Walter Schulte originally as a psycho-diagnostic test to study the properties of attention. It is a grid (generally size 5x5) with randomly distributed numbers or letters. There are possible variations with different dimensions, coloured cells and values.
Focus on the grid centre and find all the numbers (letters) with your peripheral vision, i.e. without moving your eyes.
Positive effects include attention stability, improved visual perception, improved peripheral vision and development of speed reading.
You can use it for training or just for fun (with positive effect). There are different sizes, styles of grid and other settings, also you can check your stats with best results.