You may use abilities that play as fast effects multiple times before sacrificing the permanent, such as Knight of Dusk's " Your Hand - A Precious Resource Of the three cards you draw at one time, only the top card is revealed, and that card is considered your hand
Then that player discovers X, where X is its mana value
Those both go to your hand, but guaranteeing land drops is crucial, and youre probably getting some other benefit from the artifact sac outlet you used to pop the Wellspring
However, if those permanents entered in the opposite order, your maximum hand size would he twenty
Magic has no shortage of awesome artifacts worth jamming for freeperhaps a Portal to Phyrexia, or an Aetherflux Reservoir for a combo finish