TO DILUTE WHITE WINE AND MAKE IT PURPLE.
Powder gall nuts and let this stand 8 days in the white wine; and in the same way dissolve vitriol in water, and let the water stand and settle very clear, and the wine likewise, each by itself, and strain them well; and when you dilute the white wine with the water the wine will become red.
Taken from The Notebooks of Leonardo da Vinci edited by Jean Paul Richter, 1880.