Never forget.
December 18, 2013
Bitcoin price: $522.70
Down 22.9% for that day.
https://bitcointalk.org/index.php?topic=375643.msg4022997#msg4022997
Discussion
Woah I did not know it dropped 22.9% that day
I didn't know until I looked it up yesterday. It was before my time.
Here's the sauce.
https://www.statmuse.com/money/ask/bitcoin-price-december-18-2013