I was at summer camp the summer I was 12. One day after swimming all the boys were back in the cabin and neither counseller was back. There were a lot of jokes about boners amongst the boys. Peter announced that he was going to show us a really cool thing that his brother Dick had just shown him. He layed down on his bed and started rubbing his penis. After a minute he had a boner. There were seven of us all gathered around with rapt attention watching everything he did. I don't think any of us had ever masturbated at that time and had no idea what it was. This was back in 1960. Information about sex was almost impossible to get, much less pictures. When books talked about 'self-abuse' I pictured monks doing self flagilation. That certainly seemed to be self-abuse to me. Even if I had seen the word masturbation, it was never actually described so as not to give anybody any ideas.
As Peter kept rubbing his boner he started breathing harder. All of a sudden he started making noises and his penis started jumping around. After a few seconds some whitish stuff started coming out. Everybody thought that was really cool. At that point we heard the JC coming and we all started getting dressed.