How was ceiling fan speed controlled before the invention (or availability) of Triac?
The fan speed was controlled by voltage. 

Full speed occurred when full mains voltage was applied. A switched multitapped autotransformer allowed discrete lower speeds to be selected. Motor power needs are much lower at reduced fan speeds despite reduced motor efficiency. This is due to the torque speed curve of the fan load. At full speed the auto transformer is not doing any work. Hence the autotransformer can be quite small and cheap.