This is Narcissus ‘Einstein,’ also shown in the second picture of the last posting. This picture is taken on April 15 whereas the first picture was taken 3 days later, on April 18th. I had to recheck my pictures because I was pretty sure Einstein’s petals had been yellow only 3 days ago. Now they are a pristine white.
The name Narcissus comes from a mythological character named Narcissus. He fell in love with his beautiful self upon seeing his reflection for the first time in a pool. Unable to embrace his reflection/lover he pined away and the flower Narcissus grew where he died; the term narcissism also comes from this source.