The retina is the exposed surface of the brain, so if you think about a pot of gold while looking at a rainbow, then there's one at BOTH ends.

"The End of the Rainbow", by Randall Munroe, licensed under Creative Commons Attribution-NonCommercial 2.5 License

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The retina is the exposed surface of the brain, so if you think about a pot of gold while looking at a rainbow, then there's one at BOTH ends.