Is this "silent prayer" a figurative meaning? Or did they do something almost silent compared to "silent prayer"? What does it mean?
ex)Perhaps the best news about speaking to groups is that it is a learnable skill. Most people who are competent speakers today could only say a silent prayer in a phone booth at one time.
It is possible to learn how to speak aloud to large groups, it is not necessarily something which comes naturally to some people.