The figure is here:

            ?
?  __ __ __/__ __ __ __ __ __
 \|__|__|__|__|__|__|__|__|__| 
  |__|__|__|__|__|__|__|__|__|\
? |__|__|__|__|__|__|__|__|__|\?
 \|__|__|__|__|__|__|__|__|__| ?
  |__|__|__|__|__|__|__|__|__|\
? |__|__|__|__|__|__|__|__|__| ? 
 \|__|__|__|__|__|__|__|__|__|\
  |__|__|__|__|__|__|__|__|__| ?
  |__|__|__|__|__|__|__|__|__| 
  /              /  /  /  / 
 ?              ?  ?  ?  ? 

To guard against any notational confusion, you may confirm that the number of cells in each diagonal, going around CW the top, is: (3, 1, 2, 4, 6, 1, 2, 3, 4, 8, 9, 2, 5, 8). Also, note that some cells are present in two diagonals and so contribute twice to the grand sum of 178.

The puzzle is from the site: "Cracking the Cryptic"