Many famous people have commented on the imagination in similar ways, Mrs M. Here's one from George Bernard Shaw with the same basic message, for example...
"Imagination is the beginning of creation. You imagine what you desire; you will what you imagine; and at last you create what you will."
As regards the Verne version I offered earlier, we need to remember that - whatever he wrote - he did so, I presume, in French! Accordingly, different English speakers trying to translate the idea would put it into their own words. Thus your version is just as likely to have appeared somewhere as mine.
As to the originator of the idea, it may well be that a similar notion was expressed by a Greek philosopher or a Roman poet thousands of years ago.