Jigme Lingpa tells of a visionary encounter with Yeshe Tsogyal where she presented him with King Trisong Detsen's skull. FYI, the King was one of his previous lifetimes.
Surprisingly, she quickly takes it back, only to return with two skulls—the first one and an identical one which was an optical illusion. She demanded that he distinguish between the two. When he couldn’t, she vanished into space.
Facing such a profoundly unsolvable puzzle, Jigme Lingpa realized, once and for all, that answers are not found on the level of yes and no. He also understood that the reason for this dilemma was the ultimate unformulated (spros bral) nature of everything—both subjects and objects. But even the so-called answer of unformulatedness is also unformulated and thus, when asked a similar question, the Buddha held up a flower as an invitation into the wisdom universe of unformulatedness.