Fourth element in Lord Vishnu hand is

A lotus flower or Padma and it is held by the lower left hand. It represents spiritual liberation, Divine perfection, purity and the unfolding of Spiritual consciousness within the individual. The lotus opening its petals in the light of the Sun is indicative of the expansion and awakening of our long dormant, original spiritual consciousness in the light of god. The lotus symbolizes that god is the power and source from which the universe and the individual soul emerges. It also represents Divine Truth or Satya, the originator of the rules of conduct or Dharma, and Divine Vedic knowledge or Jnana. The lotus also symbolizes that Vishnu is the embodiment of spiritual perfection and purity and that He is the wellspring of these qualities and that the individual soul must seek to awaken these intrinsic Divine qualities from Vishnu by surrendering to and linking with Him.