In the Shiva Purana, at the beginning of time in the Cosmos, Vishnu and Brahmā approached a huge Shiva Lingam and set out to find where Shiva began and where he ended.
Vishnu was appointed to seek the end and Brahma the beginning. Taking the form of Vishnu’s 3rd avatar; the boar Varaha, Vishnu began digging downwards into the earth, while Brahma took the form of a swan and began flying upwards. However, neither could find the end or begining to Shiva. He was infinite.