What is a yeast cake? Kids and I are reading a book written in the 50's, and there's a recipe in the book that uses one "yeast cake"?  What is a suitable replacement in dry yeast?

The rest of the recipe (this is from memory) uses 1C Milk, 1 Egg, 1C flour and several other smaller amounts of flavoring/ingredients.
Bob's Red Mill website states that one cake is the equivalent to one packet of dried yeast (0.25oz or 2.25 tsp):


  One (1/4-ounce) yeast packet of dry yeast OR 1 cake fresh, compressed yeast EQUALS 2- 1/4 teaspoons dry yeast (active dry or instant active dry)