Which book says, 'Oh, that my head were a spring of water, and my eyes a fountain of tears'?

Answer: Jeremiah

Jeremiah 9:1 goes on: "I would weep day and night over the slain daughter of my people."

“Oh, that my head were a spring of water, and my eyes a fountain of tears! I would weep day and night over the slain daughter of my people.”— Jeremiah 9:1 (BSB)