What is "Woods Metal"
Here is some additional info from web

Wood's metal, also known as Lipowitz's alloy or by the commercial names Cerrobend, Bendalloy, Pewtalloy and MCP 158, is a eutectic, fusible alloy with a melting point of approximately 70 °C (158 °F). It is a eutectic alloy of 50% bismuth, 26.7% lead, 13.3% tin, and 10% cadmium by weight.

I have experience using the material for fixturing of difficult to secure /  shaped parts for machining. It can also help in fixturing/holding - then later melted away. 

The eutectic composition will privide lowest Tm and get the info from a phase diagram. 

Do not add mercury for safety reasons.