It's accumulated knowledge from years of reading, talking to someone, watching documentaries, reflecting, contemplating and meditating. the letter though I got from an acquaintance years ago and I don't know where he got it. I saw Einstein's riddle over the internet which took me about an hour to solve and I thought I'd write something about his letter. watch out for my next blog where I reflect on Tesla's letter to his friend if Tesla is of interest to you.