function dig(uint capsuleNumber) {
    Capsule storage capsule = depositors[msg.sender].capsules[capsuleNumber];

    require(capsule.unlockTime <= block.timestamp);
    require(capsule.withdrawnTime == 0);

    totalBuriedCapsules--;
    capsule.withdrawnTime = block.timestamp;
    msg.sender.transfer(capsule.value);
  }