The Japanese poet Ono Mo Kobachi (825 - 900 CE) wrote a tanka poem I really liked. As it was translated from Japanese, the 5-7-5-7-7 syllable pattern doesn't show. His poem:
Thinking about you,
I slept and saw you
in a dream,
If I had known it'd have been a dream,
I wouldn't have wake up.
It was the inspiration for my tanka I Must Be Dreaming. I'm considering making a chain of tankas elaborating on the idea.