What is a reasonable amount to give as a wedding gift?

The daughter of a cousin of mine is getting married. I have not spoken to the cousin in ages. She lives in California and I live on the east coast. I am going to the wedding to establish some sort of contact with my relatives. My brother has been in regular contact with some of them and will also be at the wedding. What would be a proper amount to give, neither stingy nor overly extravagant?. We are all middle class.