You control at least one Plains that enters the battlefield untapped.
There is at least one additional artifact on the battlefield.
Steps
Activate Welding Jar by sacrificing it, regenerating target artifact.
Activate Tameshi by paying ({W} magic symbol) and returning any Plains that enters the battlefield untapped to your hand from the battlefield, returning Welding Jar from your graveyard to the battlefield.
When Welding Jar enters the battlefield, Kodama of the East Tree triggers, putting a Plains from your hand onto the battlefield.
Activate the Plains by tapping it, adding ({W} magic symbol) .