F W Boreham tells this story from his travels through the Arabian desert:
One incident of the drive across the desert comes forcefully to mind today. For its water supply Arabia is largely dependent upon sea water—salt water that has been condensed. Out beside the desert road we saw the great works in which the condensing is done, with the mountains of salt standing near by. I looked at those heaps of salt and wondered. Our driver was an Arab; but fortunately he could speak English well.
‘I suppose,' I said, leaning forward and addressing him, 'I suppose that this is salt of a crude kind to be used for agricultural purposes, or something of the kind?'
‘No,' he replied, looking quite pained, 'it's beautiful salt; what's wrong with it.’
I felt very humiliated and half resolved to drop the subject; but I was still puzzled, and decided to venture once more. ‘This salt,' I said, 'will probably have to go through several processes yet before it is ready to be shipped away as table salt?'
‘No,' he answered, looking even more hurt than before, 'it's perfect. What's wrong with it?'
I felt crushed but eventually made up my mind to make one more attempt to satisfy my curiosity. ‘You must really forgive me,’ I pleaded, humbly, ‘but if this salt is such beautiful salt, how do you account for its strange browny colour?’
And then my wife, whom I always carry with me to deliver me from such embarrassments, nudged me gently, and enquired, ‘Have you forgotten that you are wearing those amber glasses?’
Indeed I had! Before setting out across the desert a friend had warned me that the glare of the sun would blind me unless I wore coloured glasses. He gave me his. They fitted so perfectly that I had forgotten that they were there; and so the salt, that was really as white as driven snow, looked brown and unclean in my sight.
And ever since that drive across the desert, whenever I hear people complaining that there is something wrong with the world, or _____________ (fill in the gap) I have remembered my own experience with the amber glasses, and have thought my own thoughts."
Source: F. W. Boreham, Arrows of Desire.
Image: Salt in the desert