by Swami Sivananda
Nishkamya Karma Yoga or the performance of disinterested works is Bahiranga Sadhana, which leads you to meditation on Aham Brahma Asmi. Karma is more external than the four means of salvation, Sadhana Chatushtaya. The four means are more external than Sravana. Sravana is more external than Manana or reflection of what is heard through a teacher or books. Manana is more external than Nididhyasana. Antaranga Sadhana is Nididhyasana or deep meditation on Aham Brahmasmi and its meaning. In Ashtanga Yoga of Patanjali Maharshi also you have the Bahiranga and Antaranga Sadhana. Yama, Niyama, Asana, Pranayama and Pratyahara are the Bahiranga Sadhana; while Dharana, Dhyana and Samadhi are Antaranga Sadhana.