The king and his daughter

Once upon a time there lived a king. The king had a beautiful daughter. Everything the girl touched, would melt. No matter what, metal, wood, plastic, etc. Everything she touched would melt! Because of this, men were afraid of her and nobody would dare to marry her. One day a wizard told the king "If your daughter touches one thing that would not melt in her hands, her symptom will be cured." The king was overjoyed. The next day, he held a competition, any man that can bring her daughter an object that would not melt, gets to marry her and inherit the king's wealth.

Three young princes took up the challenge. The first prince brought a huge diamond, thinking that diamond is the hardest and will not melt. But alas, once the princess touched it, it melted! The prince went away sadly.  

The second prince brought a very hard alloy but the same thing he too went away.

The third prince told the princess "Put your hand in my pocket and feel it" The princess did as told, though turning red. It did not melt!!! The king was overjoyed !!! And, the third prince lived happily with the princess forever after.......

What was the object ?????