This should be one of luckytrim's trivia questions......
HINT
:"???????????" was a song written and performed by the band Pink Floyd for their album Soundtrack from the Film More. It appeared in shortened form in the live suite The Man and the Journey, where it was entitled "Sleep". ...
en.wikipedia.org
mercury: a heavy silvery toxic univalent and bivalent metallic element; the only metal that is liquid at ordinary temperatures
erratic: liable to sudden unpredictable change; "erratic behavior"; "fickle weather"; "mercurial twists of temperament"; "a cool and willful at one moment, utterly fragile the next"
wordnet.princeton.edu/perl/webwn
When you figure it out. Please DO NOT type it. For personal reasons, for now. Thank you.