What is meant by "the pleasant mount" in the hadith, and does it refer to horses or camels in the time of the Prophet, and what is the unpleasant mount?

The term "comfortable mount" (al-markab al-hanee') in the hadith "Four Things are from Happiness" refers to a comfortable and easy conveyance that does not cause hardship or fatigue, and allows the rider an opportunity to remember Allah Almighty. In the past, this included riding animals and ships. Today, it extends to modern means of transport such as cars. All of these are blessings from Allah upon His servants, and their ruling regarding gratitude and the remembrance of riding is the same.