Mishna Perek 5

(12) There are four types of students:

• Quick to learn and quick to forget--his gain is canceled by his loss.
• Difficult to learn and difficult to forget--his loss is canceled by his gain.
• Quick to learn and difficult to forget--smart.
• Difficult to learn and quick to forget--this is a bad portion.

(15) There are four types who sit before the sages:

the sponge,

the funnel,

the strainer,

and the sieve.

The sponge - because it absorbs everything;

the funnel - because it let's in at one end and out the other;

the strainer - because it lets the wine out and retains the sediment;

the sieve - because it lets out the bran and retains the fine flour.