From the notebooks of Leonardo da Vinci:
“OF SELECTING THE LIGHT WHICH GIVES MOST
GRACE TO FACES.
If you should have a courtyard that you can at pleasure cover with a linen awning, that light will be good. Or, when you want to take a portrait, do it in dull weather, or as evening falls, making the sitter stand with his back to one of the walls in the courtyard. Note in the streets, as evening falls, the faces of the men and women, and when the weather is dull, what softness and delicacy you may perceive in them. Hence, O Painter! have a court arranged with the walls tinted black and a narrow roof projecting within the walls. It should be 10 braccia wide and 20 braccia long and 10 braccia high and covered with a linen awning; or else paint a work towards evening or when it is cloudy or misty, and that is the perfect light”
A braccia is the length of your arm, about 2 feet. It sounds like a giant soft box where the artist and the subject get inside and work with soft toplight. This light was the norm in early Italian photo studios. Note photo of a Florentine studio from the around the year 1890.