It's a few years from now, and an incredible breakthrough in medical science has occurred that allows doing an in-depth 3D analysis of a deceased person's body, allowing their brains and bodies to be restored with most memories and personality intact using copious quantities of handwavium. The procedure generally works as long as a body is still reminiscent of a human being, and they would have to be only slightly better preserved than the Children of Llullaillaco. Assuming an ancient culture wanted to preserve a then-healthy human being (of any age or gender) for as long as possible...
What is the most ancient society which was capable of this, allowing preservation of a body with minimal decomposition long enough for our modern handwavium-based necromancy?
Could the ancient Romans in particular near the end of the Roman Empire have done things, for example by sailing to a location cold and dry enough (even if they do not return)?
Could any other society around that time accomplish this? The method of preservation does not need to be specifically cryogenic, as long as they could have accomplished the feat.