Never stare directly at the Sun as your eyes may permanently be damaged!
The Mercury transit will NOT be visible to the naked eye!
In order to observe the Mercury transit, it is recommended to use a small telescope equipped with a dedicated solar filter in front of the telescope's opening. The safest way to observe the transit is to project the solar image onto a white sheet of paper. This is the so-called "projection method", and it is used by telescope observers here at Uccle.
If you want to verify anyhow that Mercury is not visible to the naked eye, please use the standard eclipse glasses or a welder’s glass 14. NEVER stare directly into the Sun without any of these two protection devices!