Left: part of a drawing made at Locarno, showing that the spot with penumbra designated 104 was counted three times (weight 3); the inset shows the same spot from Mt. Wilson. Right: two spots with the same area on drawings from Mt. Wilson and counted with weight 1 by Wolfer, in each case as one group with one spot (Wolf’s notation: groups.spots = 1.1), as the group was the only group on the disk.