Severe Hindi austerities in Kali Yuga?

[Dean Michael Anderson]

We were discussing the Hindu legends about severe austerities performed by Dhruva, Parvati, etc. and it came up that some Hindu scriptures say that they are not appropriate for Kali Yugi, i.e. the age that we are said to be in now.
But no one could remember the source of that comment about their obsolescence. Does anyone have sources for this?
Best,
Dean AndersonEast West Cultural Institute