Grand Master Miao-lê states in his Summary of the Great Concentration and Insight:

“The theoretical study and the spiritual contemplation of the T’ien-t’ai School is founded on the thoughts of Nāgārjuna. Since Zen Master Hui-wen in the Northern Chi Dynasty merely presented the ‘three wisdoms and threefold contemplation,’ the correct wisdom has been attained by meditation of the Lotus Sūtra, both theoretical study and spiritual contemplation have been widely discussed, and the content of the spiritual contemplation has been well arranged since the time of Nan-yüeh and T’ien-t’ai. If a person wants to practice the spiritual contemplation according to the Lotus Sūtra, he should decide the content of practice after establishing the clear answer to the issues on the provisional and true teachings, and on the essential and theoretical sections. Since the Lotus Sūtra is the sole scripture worthy of being called ‘Wonderful,’ the way of the spiritual contemplation should be established according to this sūtra. ‘Five expedients’ as preparatory practice and the ten-stage, ten-objective way of observing mind are indeed the perfect and sudden (Tendai) meditation based entirely on the Lotus Sūtra. Therefore, the perfect and sudden meditation is merely another name of meditation on the Lotus Sūtra (since it is the way of practicing the spiritual contemplation based on the truth of the Lotus Sūtra).”

Risshō Kanjō, A Treatise on Establishing the Right Way of Meditation, Writings of Nichiren Shōnin, Doctrine 2, Page 221