Narada Purana (Jyotisha Selections) · by Vyasa
Chapter 6 · Calendar, Muhurta Elements
कालमानं मुहूर्ताङ्गानि च
कट्यामुन्मत्तता नाभौ च्युतिः पुच्छे ध्रुवं जयः ।स्थिराणि मध्यमान्येषां मध्यनागचतुष्पदौ ॥ २२३ ॥
In the full Narada Purana (Purva Bhaga) this is chapter 56, verse 223.
The waist may bring a risk of a disturbed mind. The navel may bring a fall. The tail brings sure victory. The fixed ones are middling. Of these, the middle ones are Naga and Chatushpada.
Simple meaning: In Vishti, the waist part may disturb the mind, the navel may bring a fall, the tail sure victory.
Classical view, not medical advice.
दिवामुहूर्ता रुद्राहिमित्रपितृवसूदकम् ।
The fifteen parts of the day each have a god as lord. The list starts here.
अर्यमा भगसंज्ञश्च विज्ञेया दश पंच च ।
The fifteen day muhurtas end with Aryama and Bhaga. A second list of fifteen then begins.
धातृ इन्द्रादितीज्याख्या विष्णवर्कत्वष्टृवायवः ।
Each muhurta is a fifteenth part of the day, and a fifteenth part of the night.