In India and Nepal and Tibet they taught about impermanence in a very straightforward way

The way it was taught in the past to Yogis was to watch someone die on the streets of India (or anywhere over there) (this was quite common in the 1980s still by the way as people often died alone on the streets and were never picked up then).

So, a master would have his disciple watch a body that had not been buried or cared for and what happened over several months to it. Though Americans being as materialistic as they are likely would go mad mostly there is a different way of looking at death in India and Nepal and Tibet often than how we see it, especially among people who are on a spiritual path there.

But, I wouldn't recommend doing this if you are an American Materialist because it just might drive you insane to watch this. Why?

Because if you identify with your body as being all you have then when you watch a human body slowly decompose while animals and bugs eat it it could destroy you as a person and give you a permanent sort of PTSD which might end your life as a functional American here on earth. 

However, a meditation on impermanence was considered one of the quickest ways to full enlightenment too as recently as the 1930s and before in places like India, Nepal and Tibet and other places in Asia.

However, if you are a real soul traveler like myself who has experienced one's soul as separate but presently joined most of the time to a physical body here on earth you might be okay with doing this.

However, I have no intention of ever doing something like this in this lifetime because I consider it counterproductive for me personally. The closest I came to something this out there was likely 4 days without water or food along the South Fork of the Trinity River in Northern California.