Started from Bengaluru to Periyakulam (Theni, Tamil nadu). You can get SETC or KSRTC buses. Bus fare - 450. It's an overnight journey. If you start by night 9.00 pm, you can reach there by morning 6.00 am. Have a fresh ingredients tea made with real cow milk in any of the tea stalls.
Trek starts from Kumbakarai falls and one can reach vattakanal via vellagavi village.
You can get bus to Kumbakarai falls from Periyakulam every two hours. Total distance is 8 kms. You can get share auto's too. If you are fit enough, you can actually walk. Have your morning breakfast in Periyakulam and pack your afternoon lunch.
Trek Permission - you can get permission on spot in Kumbakarai falls and they charge 250₹ and another 250₹ if you need a guide.