In the vedic ceremony the paraphernalia required for the sacrificial ceremony includes five kinds of powder, five kinds of leaves, five kinds of cow products, five kinds of grains and five kinds of jewels. So these are required for offering to the sacrifice: Five items of five kinds. So because we cannot collect all these things conveniently, we simply are satisfied with five kinds of powders. In the vedic system also when eatables are offered to somebody, five varieties of dishes are offered. Another significance of the vedic system is that arbitration is also made of five men. So this "five'' is mentioned in many places. Just like in devotional service. Narada has written also five kinds of literatures; They are called Narada pancaratra. So it is traditional vedic system. What for they were made in routine in terms of "five'' that is very difficult to find out but traditionally it is followed by vedic disciples as far as possible.
Letter to Satsvarupa, 25 August, 1971