Narada Purana (Jyotisha Selections) · by Vyasa
Chapter 9 · Vastu, Griha Pravesha
वास्तु गृहप्रवेशश्च
ब्रह्मभागाः पिशाचांशाः शिराणां यत्र संहतिः ।तत्र तत्र विजानीयाद्वास्तुनो मर्मसंधयः ॥ ५५७ ॥
In the full Narada Purana (Purva Bhaga) this is chapter 56, verse 557.
The Brahma parts, the pishacha (goblin) parts, and the places where the veins meet: know these as the plot's vital points and joints.
Simple meaning: The middle parts, the goblin parts and where the veins cross are the plot's weak spots.
मर्माणि संधयो नेष्टाः स्वस्थेऽप्येवं निवेशने ।
Avoid vital points and joints. Good months are Margashirsha, Phalguna, Vaishakha, Magha, Shravana and Kartika.
मासाः स्युर्गृहनिर्माणे पुत्रारोग्यधनप्रदाः ।
These months bring sons, health and wealth. Each letter group of the alphabet has its own direction.
खरोश्वोथ हरिः श्वाख्यः सर्पाखुगजशाशकाः ।
Each letter group has an animal. The fifth group from your own is your enemy.