Karmandir 
About
The Chandra Yantra is the number yantra of Chandra dev, also called Soma, the Moon. Its nine numbers run from 2 to 10: each is one more than in the Surya Yantra, so every row, every column and both diagonals add up to 18, with 6 in the middle. In the full Navagraha Yantra, Chandra's square sits in the south-east corner, the place the Matsya Purana gives him in the Navagraha mandala. Families keep it in the puja place and remember Chandra dev on Mondays with his verse from the Navagraha Stotram, which praises him as white like curd, conch and snow.
Parts of the yantra
Number square: nine cells, written in Devanagari digits in the drawing — top row 7, 2, 9; middle row 8, 6, 4; bottom row 3, 10, 5. Every row, column and diagonal totals 18, and 6 sits in the middle cell. Any two numbers facing each other across the middle always add up to 12. Lines: a gold outer line closes the square and saffron lines divide it into nine cells. Frame: a plain border of three lines around the square, marking the yantra's space.
How to use it
Place the yantra upright on a clean cloth in the puja place. On a Monday, or on any day, light a diya, offer a flower and sit quietly facing it. Rest your eyes first on the middle number, 6, then move them through the numbers from 2 up to 10, one cell at a time; this gives the mind one calm thing to follow. Then read Chandra dev's verse from the Navagraha Stotram (दधिशङ्खतुषाराभं…) once, or 11 times. Wipe the yantra with a soft, dry cloth to keep it clean.
दधिशङ्खतुषाराभं क्षीरोदार्णवसंभवम्। नमामि शशिनं सोमं शम्भोर्मुकुटभूषणम्॥
Dadhishankha Tusharabham Kshirodarnava Sambhavam. →
Frames differ from print to print: the NCERT figure, for example, draws this square inside a circle. Many prints use the digits 1, 2, 3 instead of the Devanagari digits used here. The numbers and their places stay the same.
