The one you would keep no matter what: the top-ranked, the rarest, the one with the trait everybody wanted. Borrowed from sneaker and watch collecting, where it means the same thing, and applied to pictures from 2021. A grail was the item you said you would never sell, and the record notes that the word was used most often by people explaining why they had just sold one.
My grail was a penguin with a specific scarf. I did not get it. Someone else did, and I still look at it occasionally, which is either collecting or something the record would rather not name.
A 2021 tweet, 'finally got my grail', with a picture of an ape in a particular hat, and the replies quoting the price. The record notes the hat and declines to state the figure.
A grail is defined by the collector, not the collection; the record's note is that in NFTs the two usually agreed, because the collector had looked up the rank first.
The record is wrong. Show what it should say, and why.
