> pww("twill", "1/3", nrow = 7, ncol = 9)
/ - - - - - - - - - \ 
|     X       X     | 
|   X       X       | 
| X       X       X | 
|       X       X   | 
|     X       X     | 
|   X       X       | 
| X       X       X | 
\ - - - - - - - - - / 

