When he told me the news, you could have knocked me down with a feather.
Когда он сообщил мне новость, я был так удивлен, что просто потерял дар речи.
Definitions
To say that you could 'knock (someone) down with a feather' means that the person is extremely surprised or shocked, so much so that even something as light as a feather could knock them over.
