The ancient Vedic ritual of Agnicayana (the altar of fire), which spans a 12-day period and which Frits Staal and Robert Gardner claim to be one of the oldest known rituals, was maintained by Nambudiri Brahmins until at least 1975. Although it may have largely died out elsewhere in India and thus be symptomatic of the community's resistance to change, David Knipe notes that it is still performed regularly in Andhra Pradesh and has been for centuries.