Do we have anything written by the Buddha himself; or you have guessed it simply in your imagination?
I purely love the question because I purely love the answer that I come up with, i.e., yes, we have simply guessed it in our imaginations.
Of course there is nothing written by Gautama Buddha himself any more than there is anything written by Jesus himself or, for all I know, Mohammad himself. Everything was written after the fact, usually out of a strong oral tradition, by disciples and friends and adherents. So it's all second hand at best.
And even those who get the word straight from the horse's mouth -- who heard some exalted poo-bah uttering one pearl or another ... STILL we "guessed it" in our imaginations. And so it goes in all spiritual endeavor. Anything called "authentic" is not yet authentic because the one hearing it has not yet put it to the test.
I think this small bit of information should be mandatory in all classes or temples purporting to disseminate so-called religion: The teaching may be very fine indeed, the pointers may be very fine indeed, the wisdom may be very fine indeed ... but it's all second-hand stuff in a world where people yearn to live authentic and peaceful lives ... you know, living first-hand, so to speak.
Calling teachings second-hand stuff is not an insult. It is just an observation. Second-hand stuff can have wonderful pointers and directions. But it needs to be admitted that, yes, we guessed it in our imaginations ... right up until we put it to the test. No more second-hand lifestyle!
Guessed it in our imaginations ... I love that.