Guild Wars 2

In order to have a chance of getting a legendary weapon do I need to be placing 4 exotic weapons or can they be the rare yellow kind?

Legendary weapons are crafted, they are not randomly given out by the forge. See this page for more detail:

http://wiki.guildwars2.com/wiki/Legendary

However, the Precursor weapon for each legendary is obtained in the manner you described. For a chance at a precursor, you must put 4 exotic or rare weapons, level 76 r higher, all of the same type of the weapon you want (I.e. mace for mace, sword for sword, etc.). This gives an extremely low chance at getting a precursor back.

Ok, thank you! I appreciate the help.