Slightest glimpse of ball or fingers as pitcher assumes grip and goes into wind - up can tip off the opposing team what to expect next. (si.com)
Move it about 15 degrees to the side (so your hand lines up with your shoulder), and up about 5 - 10 degrees (so that the background shifts a little and you get an ever - so - slight glimpse of the top of your head). (imore.com)
When mystics have caught the slightest glimpse, they have been beside themselves. (faith.org.uk)