The Angel's Crown
The taste of the Angel's Crown mushroom has never been described consistently. It has been called subtle, delicate, sublime. Gourmets across the world have sampled it, and compared it with a hundred delicacies, favourably but vaguely. The delight of eating it is incomparable, but eludes the memory. Within hours, all that remains is a sense of having enjoyed it, but no sensory trace remains in the mind.
Perhaps if one could taste it a second time, one could say more. But it is a once-in-a-lifetime experience; a second exposure is fatal within minutes.
(Thanks to Saladin Ahmed for this #writing prompt: https://twitter.com/saladinahmed/status/854662901533216768)