Canto 1 - Boyhood
Bāla-kāṇḍa
Chapter 7: King Daśaratha’s Ministers
Text 1.7.3

धृष्टिर्जयन्तो विजयः सिद्धार्थो ह्यर्थसाधकः।
अशोको मन्त्रपालश्च सुमन्त्रश्चाष्टमोऽभवत्॥

dhṛṣṭir jayanto vijayaḥ siddhārtho hy arthasādhakaḥ
aśoko mantrapālaś ca sumantraś cāṣṭamo ’bhavat

dhṛṣṭiḥ = Dhṛṣti; jayantaḥ = Jayanta; vijayaḥ = Vijaya; siddhārthaḥ hi = Siddhārtha; arthasādhakaḥ = Arthasādhaka; aśokaḥ = Aśoka; mantrapālaḥ = Mantrapāla; ca = and; sumantraḥ ca = and Sumantra; aṣṭamaḥ abhavat = they were.

They were: (1) Dhṛṣti, (2) Jayanta, (3) Vijaya, (4) Siddhārtha, (5) Arthasādhaka, (6) Aśoka, (7) Mantrapāla and (8) Sumantra.

Śrī Vālmīki enlists the ministers here. Counting Dhṛṣṭi as the first, Sumantra is the eighth.