One of the important features in early Tiantai texts remains to be examined is the emphasis on Si nianchu (四念處，smrty-upasthana) in these texts. Si nianchu is not only an essential element in Huisi’s Dharma-Gate of the Samadhi Wherein All Dharmas are Without Dispute (Zhufa Wuzheng Sanmei 諸法無諍三昧，T. 1923) but also serves as a framework of Huisi’s Samadhi of Freely Following One’s Thought (Suiziyi sanmei 隨自意三昧，XZJ 98). Huisi’s discussion of Si nianchu in the Dharma-Gate of the Samadhi Wherein All Dharmas are Without Dispute can actually be seen as a way through which he approaches and understands the Moho boruo boluomi jing (摩訶般若波羅蜜經，Pabcavijwatisahasrika Prajbaparamita) and the Da zhi du lun (大智度論 Prajbaparamitopadewa or MahaPrajbaparamita-sutra-upadewa). As one of the earliest historical figures who practiced the above Mahayana sutras as well as the Bozhou sanmei jing ( 般舟三昧經 Pratyutpanna-BuddhaSajmukhavasthita-Samadhi-sutra), Shoulengyan sanmei jing (首楞嚴三昧經，Wurajgamasamadhi-sutra), and Miaofa lienhua jing (妙法蓮華經，Saddharmapundarika), Huisi’s interpretations of the Si Nianchu may not only provide clues for his readings of these sutras, but also shed new lights on our understanding of the practice of Mahayana meditation in the sixth century China.
