Here's an interesting one: this 1928 Milo Barbell advertisement features Mr. Al Manger, who built himself up from "a bag of bones" into a weightlifting champion with the power of sensible physical training and a Milo weight set. At the age of 21, Manger weighed only 97 pounds, and within a year of barbell training, had added 26 pounds of solid muscle.
Manger kept at it, and went on to win three national lifting championships, one in the 181 lb. class in 1929 and two light-heavyweight crowns in 1930 and 1932. Manger finished fifth with a 315 kg. total at the 1932 Los Angeles Olympic games. Manger also won regional championships in the shot put and weight throwing.
...Pretty good for a skinny kid from Baltimore.
If you would like to learn about the specific types of training that helped Manger build his strength, you'll find it in The Alan Calvert Collection.