why is mercury usually hard to see without a telescope?

Mercury is hard to see from Earth because it's so close to the bright sun. It is the closest planet to the sun and the smallest of all the 8 big planets. Mercury is only a little bigger than Earth's moon.

mark twain, real name samuel langhorne clemens, was an american writer, humorist, entrepreneur, publisher, and lecturer. among his novels are the adventures of tom sawyer and its sequel, the adventures of huckleberry finn, the latter often called "the great american novel". wikipedia