I like the idea, but I am curious as to why you have to do it in Arduino? If the premise is that stone is a long lasting substrate, why do we need to carve it with technology? Why could we not just carve it now by hand? Is it meant to be programed if a catastrophy occurs? What will today's icongraphy mean to people in the future? If there aren't envelopes in the future then how will an image of an envelope indicate mail? I think there needs to be a richer iconographic language to couple with this technology.