What is a double cube proportion box?

[TheHinge]

Hi, I am hoping one of you will be able to help me. I have a book, "Box-Making Basics" and in it it has some "classical or traditional proportions, these include the double cube, the root-of-two box, the 1:2:3 box, and the golden rectangle." (p.4)

I don't understand what the double cube is. In the picture it has 1 1 2 where the height is 1, the width is 1 and the length is 2. What does this mean? Thank you.

[Tequila]

It means two cubes next to each other. In your example, that would be two 1x1x1 boxes = one 1x1x2 box.