As the embodiment of the sun and often shown as a disc carried on a boat, Ra rose in the east in the morning, traversed the heavens and set in the west in the evening. Ra travelled into the realm of night to meet the powers of darkness in the underworld. Chief among these was Apep the serpent who tried to swallow the barque (boat). Ra, emerging triumphant in the morning sky, was offered prayers of thankfulness so that the sun would continue to shine. Ra, or Re, the sun god of Heliopolis and father of the Gods is often represented as a man with a falcon's head or simply as a falcon. The solar deity, being the most important element of Egyptian religion, was initially Horus, then Ra followed by Horus-Ra and later Amun-Ra. From the Book of the Dead: Spell 15 Hail to you Ra in your rising, O Atum-Horakhty! You are adored when your beauty is in my eyes and your rays are upon my body.You go in peace in your Night-barque, your heart is warmed by the winds in your Day-barque. You cross over the heavens in peace and your enemies are overthrown. A swallow can sometimes be seen perched on the prow of the barque as Ra passes through the underworld. The swallow is the "day greeting" bird who announced the approach of the sun. One Egyptian myth tells of the tears of Ra falling to the earth in the form of bees.