Srimad-Bhagavatam: Canto 11 - Chapter 1 - Verse 23


तद्वत् षोडशसङ्ख्याने आत्मैव मन उच्यते ।भूतेन्द्रियाणि पञ्चैव मन आत्मा त्रयोदश ॥ २३ ॥


tadvat ṣoḍaśa-saṅkhyāneātmaiva mana ucyatebhūtendriyāṇi pañcaivamana ātmā trayodaśa


According to the calculation of sixteen elements, the only difference from the previous theory is that the soul is identified with the mind. If we think in terms of five physical elements, five senses, the mind, the individual soul and the Supreme Lord, there are thirteen elements.


According to the theory of thirteen elements, the sense objects — aroma, taste, form, touch and sound — are considered by-products of the interaction of the senses and physical matter.