It is! But it's a pretty time consuming process! You may want to carve some Electrum seed into the stone and sign messages for the respective addresses from an offline machine, that way you're completely safe!
When we talk about long time curation, then is this not a great idea, its actually a terrible idea, since you will also need to consider the aspects of digital curation.
You will need to include meta data in the stone how the seed should be read and understood, this will be quite substantial, much more data than the seed itself.
You cannot assume that a compatible version of the required software can just be "downloaded" 100 years from now, actually, you cannot be sure the term download even exist.
It is reasonable to assume that the Latin alphabet exist 100 years from know, therefor can the key be preserved with reasonable chance by carving that into the stone in raw format with latin letters, if any thing more than the raw key is carved, then will you also need to include meta data. Data curation is actually much more complicated then one might think at first glimpse.