Within 5 minutes of waking, half of your dream if forgotten. Within 10, 90% is gone. The famous poet, Samuel Taylor Coleridge, woke one morning having had a fantastic dream (likely opium induced) – he put pen to paper and began to describe his “vision in a dream” in what has become one of English’s most famous poems: Kubla Khan. Part way through (54 lines in fact) he was interrupted by a “Person from Porlock“. Coleridge returned to his poem but could not remember the rest of his dream. The poem was never completed.
“In Xanadu did Kubla Khan
A stately pleasure-dome decree:
Where Alph, the sacred river, ran
Through caverns measureless to man
Down to a sunless sea.