When I started my Art Foundation Course at Wimbledon College of Art (way back in 1985), I had a conversation with my tutor where he disagreed with me.
He was firmly of the belief that it was not possible to draw something purely from the imagination.
He maintained you had to have source material.
I said that this was not necessarily true and that , if I was familiar with the subject, I could draw it purely from my imagination.
"Ok, " he said, "draw me a nun on a bicycle."
"Fine," I said," I know what a nun looks like and I know what a bicycle looks like. When do you want it?"
"Oh, by the end of the day," he said and wandered off, confident that this would not happen
An hour or so later I left this picture in his pigeon hole.