• ### Grandfathers problem

What weights more, one pound of feathers or one pound of gold?

#### Spoiler

One kg of feathers weights the same as one kg of gold. But there are two different pound measures the avoidupois and the troy system.

1 pound avoidupois = 16 ounces avoidupois = 7000 Grains
1 pound troy = 12 ounces troy = 5760 Grains

The feathers are 1260 havier.

Sam Loyd, Cyclopedia of Puzzles, 1914, p16

• ### Rhyming Classic

This riddle, one of the world's oldest, is still good for starting arguments. A man is looking at a portrait. "Whose picture is that?" someone asks, and the man replies: "Brothers and sisters have I none, but that man's father is my father's son." At whose picture is the man looking?

#### Spoiler

The portrait is of the man's son. Many people mistakenly argue that the man is looking at a picture of himself. If he had said, "... that man is my father's son." then this solution would be correct, but he said, "... that man's father is my father's son." One way out of the confusion is to substitute the word "me" for the more cumbersome phrase "my father's son." Then the statement becomes, "that man's father is me."

• ### That Old, Old Story

The old riddle starts with the host pointing to a portrait on the wall. In the modern version, which starts the same way, he might go on to say: 'Brothers and sisters have I none, but that man's father's a score and one years older than that old son-of-a-gun, whose father of course is my father's son.' Pausing a moment, he would continue: 'Forty was he when his portrait was done, two years ago by an artist for fun.'

Now, how old would the speaker be?

Hunter, Fun with Figures, Problem 122

• ### The riddle of the Sphinx

What walks on four legs in the morning, two legs in the afternoon, and three legs in the evening?

#### Spoiler

The answer is man: crawling on four "legs" in early life, walking on two legs, then using two legs and a cane in later life.

• ### A new Sphinx riddle

What can make one man blind and another man see, makes one building strong and tears another one down?

#### Spoiler

The answer to your riddle is "sand", because you can throw a handful in someone's eyes to blind them, melt the sand to make glasses to help them to see, and concrete makes buildings strong while sandstorms tear them down. But glasses and concrete are quite a bit more recent than Oedipus. Maybe they had other answers in mind, but I can't imagine sand helping someone to see until many many years after the fall of the Greeks.