Goren’s that is; but expanded usage of limit bids is one of the key innovations in modern bidding.  Here are some interesting excerpts from “The Official Encyclopedia of Bridge” regarding limit bids.

A bid with a limited point-count range, usually fewer than four points . . . normally applied only to non-forcing bids below the game level.  Opening notrump bids are invariably limited.

How wide can the limits be?  The nearer the bidding is to game, the closer the limits must be.  When the bidding reached 2NT with the possibility of 3NT; or when the bidding reaches three spades, there is no longer any margin for exploration.  So to give partner the chance of making an accurate decision, all such bids must have a range of only 2 points.  All  these (limit bids) are typically encouraging bids, indicating that partnership has a minimum of 23-24 points, and urging partner on to game if he has a little more than his promised minimum.

The discussion goes on to observe that limit bids at a lower level can afford a range of three or four points because there is more room below game to further define the hand subsequently without getting too high.  Major suit raises are the most important examples.  A simple raise from 1 heart to 2 hearts promises 6 to 9 points, while a jump raise to 3 hearts promises 11 to 12 points.  (You have to adjust 10 point hands up or down one point to conform.)  Please note that, assuming opener has a minimum of 13 points, the combined minimum becomes 24 to 25 points, just shy of the 26-point game goal.  In Goren’s day, these jump raises promises 13 points and were game-forcing.