Temporal observation was the act of viewing a non-native historical period. Various methods were employed by anthropologists, historians, and law enforcement personnel.
Historical imagery of the Human, Vulcan, and Orion civilizations was displayed by the Guardian of Forever. (TOS: "The City on the Edge of Forever"; TAS: "Yesteryear")
In 2268, the starship USS Enterprise traveled back in time to 1968 for historical research. (TOS: "Assignment: Earth")
28th century scientists observed the construction of the Great Pyramid at Giza. (ENT: "Cold Front")
In the 31st century, Daniels owned a hand-held Temporal Observatory. (ENT: "Cold Front")