Hoover Dam

{t}; {e}{e}: Add {u}{u} to your mana pool.
{t}, {u}{u}: Add {e}{e} to your energy pool.
{t}, {2}{u}, {e}{e}{e}{e}: Put an artifact token named Hoover Turbine with "{t}: Add {u} to your mana pool." onto the battlefield.
{t}, {3}{u}{u}, {e}{e}{e}{e}{e}{e}, Sacrifice 4 Hoover Turbine tokens: You get an emblem with "Whenever you tap a land for {u}, add another {u} to your mana pool."