[Bytewave81]

It's an example message proposed in a 1993 report from Sadina National Laboratories[1]. I doubt it's actually been legitimately written or used anywhere, but it's one of many such long-term messages intended to communicate danger thousands of years into the future, when the dangers of radioactive waste or even the prevailing language of the time may not be known.

[1]: https://en.wikipedia.org/wiki/Long-time_nuclear_waste_warnin...