"The fact is, we find here, and not elsewhere, a complaint which may be called `Holy Land on the Brain.' It is no obscure cerebral disorder, like the morbid delusions of the poisoner it rather delights to announce its presence, to flaunt itself in the face of fact.  This perversion of allowable sentiment is the calenture which makes patients babble of hanging gardens and parterres of flowers, when all they beheld was sere and barren.  The green sickness mostly attacks the new and unseasoned visitor from Europe and North America, especially from regions where he has rarely seen a sun.  It is a 'strange delusion that the man should believe,' Carlyle says, `the thing to be which is not.'"

This is the very phenomena that Twain deals with throughout his visit to the "Holy Land".  His pilgrim colleagues all suffer from this condition.  This is probably worth an essay on  itself.