Bṛhad-bhāgavatāmṛta Part 2 Chapter 2 Text 101

bhaktau nava-vidhāyāṁ ca
mukhyaṁ smaraṇam eva hi
tat samagrendriya-śreṣṭha-
mano-vṛtti-samarpaṇamTRANSLATION
Of the nine kinds of devotional service, remembrance is the chief. It is an offering of the activity of the mind, the most important of all the senses.