Chapter six is the Gītā’s chapter on meditation, and it begins with furniture.
At 6.11 Kṛṣṇa describes the seat: a clean place, a firm seat, neither too high nor too low, layered with kuśa grass, then a deerskin, then cloth. At 6.12: sit on it, gather the mind to one point, and practise.
The yoga mat in your cupboard has a very old ancestor.
The verses
BHAGAVAD GĪTĀ · 6.11शुचौ देशे प्रतिष्ठाप्य स्थिरमासनमात्मनः।
नात्युच्छ्रितं नातिनीचं चैलाजिनकुशोत्तरम्।।
śucau deśe pratiṣṭhāpya sthiram āsanam ātmanaḥ
nātyucchritaṁ nāti-nīcaṁ cailājina-kuśottaram
Having established for himself, in a clean spot, a firm seat that is neither too high nor too low, and covering it with cloth, deer-skin, and Kusa grass in reverse order—
BHAGAVAD GĪTĀ · 6.12तत्रैकाग्रं मनः कृत्वा यतचित्तेन्द्रियक्रियः।
उपविश्यासने युञ्ज्याद्योगमात्मविशुद्धये।।
tatraikāgraṁ manaḥ kṛtvā yata-cittendriya-kriyaḥ
upaviśyāsane yuñjyād yogam ātma-viśuddhaye
Sitting on the seat, with a concentrated mind, controlling the mind and senses, one should practice Yoga for the purification of the self.
Going deeper
The practice in chapter 6 starts with a place to sit. 6.10 says the yogi should stay in a solitary place, alone, with mind and thought controlled, free from desire and possessiveness. 6.11 then describes the seat in detail: set in a clean spot, firm, neither too high nor too low, and covered with cloth, deerskin and kuśa grass. 6.12 says what to do on it: sit with a gathered mind, hold the mind and senses in check, and practise yoga for the purification of the self. 6.13 goes on to the body, with trunk, head and neck upright, still and steady, gaze held at the tip of the nose. The order is worth noticing: the setting comes first, then the mind, then the posture. A mat in a cupboard is a small version of the same preparation. See chapter 6 for the whole passage.