The San Bartolo Mural is a art mural painted by the ancient Mayans found now in modern day Guatemala. The mural is found inside an 85 foot tall pyramid called the Las Ventanas and they were carbon dated to around 100 BC which makes it the oldest found Mayan artifact. The source depicts a Mayan maize god receiving a vine calabash while multiple other men and women follow walking and kneeling on a snake below them.
This mural tells us that Mayan society was very much surrounded and often ruled by religion and various beliefs. This source shows us the rituals and the relationships between the god and the people. Knowing that religion existed in the Mayan empire, people can infer that the Mayans may have had a rule to live by and daily routines of either praise for their god or various things they could and couldn't do. The Mayan beliefs obviously died along with the death of the people when the Spanish arrived.
The source is somewhat reliable as the mural was carbon dated and found to be during the era of the Mayan empire's existence. However what the mural depicts will never be known exactly as many elements may have been exaggerated in the mural. The usefulness, however is good as it allows modern day humans to get a glimpse of what ancient people believed and what they worshipped. This also tells as the structure of society back then.