How would I maintain the integrity of a bottle of wine buried in the ground for four years?

For leap year, I convinced a handful of people to write letters to themselves for the next leap year. The idea is to bury the letters in the ground and dig them up in four years (I live in the New England). There was this great idea to do the same with a bottle of wine. Bury it and then dig it up four years from now. However, I’m not sure the best way to do this and still maintain the drinkability of the wine in four years. Does it need be kept in an airtight container? How far down does it have to be buried in order to maintain a consistent temperature that won’t freeze.