If you can define "pure" in terms of how it relates to energy consumption, I can try. The one PoS system I'm (edit: deeply) familiar with is Ethereum 2.0's, I

If you can define "pure" in terms of how it relates to energy consumption, I can try. The one PoS system I'm (edit: deeply) familiar with is Ethereum 2.0's, I wrote about it a couple of years back: https://medium.com/@jpa_of_snc/consensus-casper-and-cryptoeconomics-in-15-minutes-or-less-c7ca2427bf88 https://medium.com/@jpa_of_snc/consensus-casper-and-cryptoec... There are testnets using this already: https://medium.com/prysmatic-labs/ethereum-2-0-phase-0-testnet-release-1e9e682db910 https://medium.com/prysmatic-labs/ethereum-2-0-phase-0-testn...