1. A method comprising: providing a probe tip of a handheld oximeter probe comprising a source structure and a detector structure, wherein an enclosure of the handheld oximeter probe comprises an elongated handle adapted to be gripped by a user and the enclosure houses a marking reservoir; providing a marking mechanism output, coupled to the probe tip of the oximeter probe at a fixed position and coupled via a supply tube to the marking reservoir contained within the enclosure, wherein the marking mechanism output is positioned at a distal end of the handheld oximeter probe and the marking reservoir is positioned proximal relative to the marking mechanism output; transmitting a first light through the source structure of the probe tip into a target tissue, wherein the marking mechanism output at the fixed position does not obstruct the transmitting of the first light from the source structure into the target tissue; receiving a second light transmitted through the target tissue at the detector structure of the probe tip, wherein the marking mechanism output at the fixed position does not obstruct the receiving of the second light through the target tissue at the detector structure; based on values for the first and second light, determining an oxygen saturation value for the target tissue; and after the determining an oxygen saturation value, causing the marking mechanism output at the fixed position to mark a tissue surface representative of a location of the target tissue.