Though the possibility of life in space, still remains an unsolved mystery, it was found that people have sketched ways to contact them as early as 150 years ago to our first attempt.
You might probably have heard of the CETI. It is Communication with Extraterrestrial Intelligence. This branch has conducted the first ever project to contact the Extraterrestrials in 1974 using a giant telescope and best technology. This telescope, named Arecibo Observatory, is an immense structure with 150m (500ft) tower to hold equipment and 1000-foot reflector dish. Even though the message was sent using such big equipment and best technology, it is expected to deliver its message after 25,000 years.
Imagine the situation 150 years back where people could not even imagine life outside the earth (UFOs were not seen that time). These were very intelligent astronomers who imagined several methods to contact aliens.
Some of them were as stupid as lighting up a 30-kilometer-wide circular canal at night after filling it with kerosene. Some were as intelligent as using a sky telegraph equipment.