Midrasch zu Mischlej 25:3

Further said Raba b. Mechasia in the name of R. Chama b. Guria who said in the name of Rab: "If all the seas were ink; all the reeds were producing pens; the expanse if heaven were sheets of parchment, and all the children of men were scribes, yet it would not suffice to write the devices of political government." What is the Biblical passage [that refers to this]? R. Mesharshia said (Pr. 25, 3.) As the height of the heavens, and the depth of the earth, so is the heart of kings unsearchable.