Draw cards equal to the number of cards in your hand, then discard a card for each card drawn this way.
Basic landcycling( , Discard this card: Search your library for a basic land card, reveal it, put it into your hand, then shuffle your library.)
11/8/2016 The number of cards in your hand is counted only as Ancient Excavation resolves. Ancient Excavation is on the stack at this time, so it’s not counted.
11/8/2016 The number of cards drawn this way might not be equal to the number of cards in your hand (for example, if you apply Necroplasm’s dredge ability instead of drawing one of those cards). The number of cards that you actually drew is what determines how many cards you discard.