The Value of Pieces

The traditional scale for piece values in chess is P=1, N=B=3, R=5, Q=9. The King doesn't have a material value, although a number of juniors I coach always say "King equals the game", which for some reason irritates me. Some people also quibble about the value of the Bishop, suggestion 3 and a quarter (or a half), as Bishops are often better than Knights.
Of course there are alternatives. One system I used in one of my computer chess programs was P=1, B=N=4, R=6 and Q=12. The aim of this system was to discourage swapping 2 pieces for a Rook and Pawn or sacing a piece for 2 pawns and a check (also known as "Coffee House compensation").
But the weirdest system I've seen recently came from a book titled "An Easy Introduction to the Game of Chess" by Benjamin Franklin, William Jones, and Francois Philidor. In this book (published in 1820) the suggested piece values are N=9.25, B=9.75, R=15 and Q=23.75. The real question of course is "What is the value of a pawn?" and the author (who I think for this section is Philidor) values the pawn as 3.75 (due to the chance of promotion), and this rises as it gets closer to the "adversery's royal line".
If you want to read this book you can do so online at Google Books. The direct link is here , and the book also contains the oft talked about (but rarely seen) "The Morals of Chess" by Dr Benjamin Franklin (Page 223)