Get last two records from table using active records

[eluser]ibnclaudius[/eluser]
How can I get the last two records from a table?

For example I have this:

id | update
1 | a
2 | b
3| c
4 | d
5 | e

I want to return it like this:

4 | d
5 | e

with order_by(id, 'DESC'), it returns:

5 | e
4 | d

How can I do this with active records?