Among the thousands of terrible images sped out to the world from the coast of Japan after the Sendai quake and tsunami, one group of images stood apart for their strange solidity and serenity. These were the views of stone tsunami markers that were made many hundreds of years ago and placed well above sea level along the coast with carved messages like this one: 'High dwellings are the peace and harmony of our descendants. Remember the calamity of the great tsunamis. Do not build any homes below this point.'

I have no idea whether these carvings are seen as art within the Japanese context. In their time perhaps they seemed as blunt and functional as street-signs do to us. But today, in their lichen-encrusted and beautifully weathered state, they've become something else: warnings from the deep past, long-distance messages. We're used to leaders and worthies erecting stone statues of themselves in order to impress future generations. But the carvers of the tsunami markers used the permanence of stone to keep a more urgent message alive through time.

There's something inspiring about the idea that people five centuries ago not only thought about the residents of the twenty-first century, but had our best interests at heart.