Akshamala Upanishad — Mantra 14
रुद्राक्षं शिवमन्त्राणां तुलसी हरिमन्त्रके। स्फटिकं सर्वमन्त्रेषु अष्टोत्तर शतं सदा॥
Rudrākṣaṁ śiva-mantrāṇāṁ tulasī hari-mantrake, sphaṭikaṁ sarva-mantreṣu aṣṭottara-śataṁ sadā
Rudraksha for Shiva mantras, tulsi for Hari mantras, crystal (sphatika) for all mantras universally — always one hundred and eight (108) beads.