Cut a strip of good paper, about 2 x 8 inches.
Leave a white strip at one end and paint the rest of the paper very light (2).
Dry thoroughly between layers.
Leave a strip of number 2 next to the white and paint the rest medium light (3).
Keep leaving a strip of the previous layer and darkening the rest till you have 10 patches with white on one end and black on the other.
Try to make uniform value jumps with each layer, but don't worry if it's not perfect. It will still work.
You don't need the numbers on your scale.