There was no indentation for a spoon because, until the introduction of granulated and cubed sugar in the late 19th century, sugar came in tall, conical, solid ‘loaves’ which varied in size considerably according to the sugar grade, and from which pieces were broken off with special iron sugar-cutters (sugar nips) shaped something like very large heavy pliers with sharp blades attached to the cutting sides. The broken pieces of the sugar loaf were then placed into the sugar bowl or basin or box, from whence they were removed with sugar tongs.
When powdered sugar was called for in a recipe, the cook had to use a mortar and pestle, or possibly a spice-mill. Some sugar-boxes had compartments for powdered sugar alongside the lumps. Finely sifted sugar could also be used in a caster, or sprinkler.
See:
http://www.oldandinteresting.com/sugar-nippers.aspxFred.