Answer:
Gold coin
Step-by-step explanation:
In Chapter 36, we see that Ahab offers an enormous reward to whoever is able to spot the white whale. This is a gold coin. This coin is a Spanish ounce of gold, or a gold doubloon. Ahab nails this coin to the mast in order to encourage his men. The large reward and the intensity with which Ahab offers it contribute to developing the idea that Ahab is extremely committed and motivated to catch this whale.